JavaScript acrobatics: This code uses eval, how to remove it? - javascript

This partial code I hacked in to JamieMThomas's JQuery plugin that combines the Microsoft JQuery template and linking plugins together (declarative linking in the templates). I wanted to reference a variable tree like "A[0].B[0].C[0].myProperty". You can skip down to the bottom as I just put this in for reference:
var extVar = $.extend({ name: elem.name },
{ convert: binding.converter.convertBack,
convertBack: binding.converter.convert });
// binding.field is a string pointing to a variable to map
var a = binding.field.match(/([A-Z]+)\[\d+\]/g); // Find all array references
// If we have arrays, we need to create the corresponding hierarchy in "mapping"
if ( a != null)
{ b = mapping; // mapping (object) will reference a variable to map
for( i = 0; i < a.length; i++) // for each array found
{ var arr = a[i].match(/[A-Z]+/); // array's name
b[arr] = []; // make mapping match our binding.field text
var idx = a[i].match(/\d+/g); // index value
if( a[i+1] !== undefined ) // is the next item an array?
b[arr][idx] = []; // Yes, match the array
else
b[arr][idx] = {}; // No, match an object
b = b[arr][idx] ; // Reference LPC[x] // reference the next child
}
}
eval('(mapping.' + binding.field + ' = eval("extVar") )');
This eval at the bottom ends up running the below code. How would you rewrite this to not include the eval statement?
mapping.A[2].B[1].C[5].myProperty = A[2].B[1].C[5].myProperty;

In javascript, just as you can do object[propertyName] to read stuff you can do object[propertyName] = value to assign stuff.
The rest is here: How to turn this JavaScript string "myArray[0].myPrice" in to a reference to myPrice?
Basically:
var data = mapping,
chain = binding.field.split(/[\.\[\]]+/);
// If the last character of binding.field is `]` we'll get "" in the end of chain
if (!chain[chain.length - 1]) {
chain.splice(-1);
}
var n = chain.length;
for (var i = 0; i < n - 1; i++) {
data = data[chain[i]];
}
data[chain[n - 1]] = extVar;
// Embrace JavaScript Awesomeness!

Related

JavaScript Search and Loop - doesn't return correct values

Please, can you check my code where is the error? It should loop trough 1 array to choose each string and then loop through second array and check, if the value from second string contains value of first string.
for (var i = 0; i < oldLines.length; i++){
var subStringEach = oldLines[i];
var subStringEachNoDash = subStringEach.replace(/[^a-z0-9]/g,'');
// read New URLs and line by line save them as an object
var newLines = $('#newUrl').val().split(/\n/);
var newUrlResult = [];
for (var j = 0; j < newLines.length; j++){
var newUrlString = newLines[j];
var newUrlStringNoDash = newUrlString.replace(/[^a-z0-9]/g,'');
var isThere = newUrlStringNoDash.search(subStringEachNoDash);
if (isThere !== -1 ) {
newUrlResult[i] = newLines[j];
}
else {
newUrlResult[i] = "";
}
}
stockData.push({OldURL:oldLines[i],SearchSubstring:subStringEach,NewURL:newUrlResult[i]});
}
Now it finds only part of the results.. I place to first array:
anica-apartment
casa-calamari-real
ostrovni-apartman
and to the second array:
http://tempweb3.datastack.cz/be-property/anica-apartment/
http://tempweb3.datastack.cz/be-property/ostrovni-apartman/
http://tempweb3.datastack.cz/be-property/st-michael-apartment/
http://tempweb3.datastack.cz/be-property/casa-calamari-real/
and it will only find and return casa-calamari-real, http://tempweb3.datastack.cz/be-property/casa-calamari-real/ and the others returns empty..
Any ideas please?
Here is the full code on Codepen: https://codepen.io/vlastapolach/pen/VWRRXX
Once you find a match you should exit the inner loop, otherwise the next iteration of that loop will clear again what you had matched.
Secondly, you should use push instead of accessing an index, as you don't know how many results you will have. And as a consequence you will need to relate the find string with it (because i will not be necessary the same in both arrays)
So replace:
if (isThere !== -1 ) {
newUrlResult[i] = newLines[j];
}
else {
newUrlResult[i] = "";
}
with this:
if (isThere !== -1 ) {
newUrlResult.push({
searchSubstring: subStringEach,
newURL: newUrlString
});
break; // exit loop
}
At the end, just output newUrlResult.
NB: If you want to leave the possibility that a search string matches with more than one URL, then you don't need the break. The push will then still prevent you from overwriting a previous result.
I see that you solved already) But maybe you will like this code too)
newUrlResult variable could be a string I guess, because loop breaks when one value is found. If no values where found there will be just empty string. And I'm not sure you need to call newLines = $('#newUrl').val().split(/\n/) on every iteration.
var stockData = [];
oldLines.map(function(oldLine){
var cleanOldLine = oldLine.replace(/[^a-z0-9]/g,''),
newLines = $('#newUrl').val().split(/\n/),
newUrlResult = '';
for (var j = 0; j < newLines.length; j++){
var newLine = newLines[j],
cleanNewLine = newLine.replace(/[^a-z0-9]/g,''),
ifExists = cleanNewLine.search(cleanOldLine);
if (ifExists !== -1) {
newUrlResult = newLine;
break;
}
}
stockData.push({OldURL:oldLine, SearchSubstring:cleanOldLine, NewURL:newUrlResult});
});

Loop, get unique values and update

I am doing the below to get certain nodes from a treeview followed by getting text from those nodes, filtering text to remove unique and then appending custom image to the duplicate nodes.
For this I am having to loop 4 times. Is there is a simpler way of doing this? I am worried about it's performance for large amount of data.
//Append duplicate item nodes with custom icon
function addRemoveForDuplicateItems() {
var treeView = $('#MyTree').data('t-TreeView li.t-item');
var myNodes = $("span.my-node", treeView);
var myNames = [];
$(myNodes).each(function () {
myNames.push($(this).text());
});
var duplicateItems = getDuplicateItems(myNames);
$(myNodes).each(function () {
if (duplicateItems.indexOf($(this).text()) > -1) {
$(this).parent().append(("<span class='remove'></span>"));
}
});
}
//Get all duplicate items removing unique ones
//Input [1,2,3,3,2,2,4,5,6,7,7,7,7] output [2,3,3,2,2,7,7,7,7]
function getDuplicateItems(myNames) {
var duplicateItems = [], itemOccurance = {};
for (var i = 0; i < myNames.length; i++) {
var dept = myNames[i];
itemOccurance[dept] = itemOccurance[dept] >= 1 ? itemOccurance[dept] + 1 : 1;
}
for (var item in itemOccurance) {
if (itemOccurance[item] > 1)
duplicateItems.push(item);
}
return duplicateItems;
}
If I understand correctly, the whole point here is simply to mark duplicates, right? You ought to be able to do this in two simpler passes:
var seen = {};
var SEEN_ONCE = 1;
var SEEN_DUPE = 2;
// First pass, build object
myNodes.each(function () {
var name = $(this).text();
var seen = seen[name];
seen[name] = seen ? SEEN_DUPE : SEEN_ONCE;
});
// Second pass, append node
myNodes.each(function () {
var name = $(this).text();
if (seen[name] === SEEN_DUPE) {
$(this).parent().append("<span class='remove'></span>");
}
});
If you're actually concerned about performance, note that iterating over DOM elements is much more of a performance concern than iterating over an in-memory array. The $(myNodes).each(...) calls are likely significantly more expensive than iteration over a comparable array of the same length. You can gain some efficiencies from this, by running the second pass over an array and only accessing DOM nodes as necessary:
var names = [];
var seen = {};
var SEEN_ONCE = 1;
var SEEN_DUPE = 2;
// First pass, build object
myNodes.each(function () {
var name = $(this).text();
var seen = seen[name];
names.push(name);
seen[name] = seen ? SEEN_DUPE : SEEN_ONCE;
});
// Second pass, append node only for dupes
names.forEach(function(name, index) {
if (seen[name] === SEEN_DUPE) {
myNodes.eq(index).parent()
.append("<span class='remove'></span>");
}
});
The approach of this code is to go through the list, using the property name to indicate whether the value is in the array. After execution, itemOccurance will have a list of all the names, no duplicates.
var i, dept, itemOccurance = {};
for (i = 0; i < myNames.length; i++) {
dept = myNames[i];
if (typeof itemOccurance[dept] == undefined) {
itemOccurance[dept] = true;
}
}
If you must keep getDuplicateItems() as a separate, generic function, then the first loop (from myNodes to myNames) and last loop (iterate myNodes again to add the span) would be unavoidable. But I am curious. According to your code, duplicateItems can just be a set! This would help simplify the 2 loops inside getDuplicateItems(). #user2182349's answer just needs one modification: add a return, e.g. return Object.keys(itemOccurance).
If you're only concerned with ascertaining duplication and not particularly concerned about the exact number of occurrences then you could consider refactoring your getDuplicateItems() function like so:
function getDuplicateItems(myNames) {
var duplicateItems = [], clonedArray = myNames.concat(), i, dept;
for(i=0;i<clonedArray.length;i+=1){
dept = clonedArray[i];
if(clonedArray.indexOf(dept) !== clonedArray.lastIndexOf(dept)){
if(duplicateItems.indexOf(dept) === -1){
duplicateItems.push(dept);
}
/* Remove duplicate found by lastIndexOf, since we've already established that it's a duplicate */
clonedArray.splice(clonedArray.lastIndexOf(dept), 1);
}
}
return duplicateItems;
}

Create variables based on array

I have the following array and a loop fetching the keys (https://jsfiddle.net/ytm04L53/)
var i;
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
for (i = 0; i < feeds.length; i++) {
var feed = feeds[i];
alert(feed.match(/\d+$/));
}
The array will always contain different number of keys, What I would like to do is either use these keys as variables and assign the value after the : semicolon as its value or just create a new set of variables and assign the values found on these keys to them.
How can I achieve this? so that I can then perform some sort of comparison
if (test_user > 5000) {dosomething}
update
Thanks for the answers, how can I also create a set of variables and assign the array values to them? For instance something like the following.
valCount(feeds.split(","));
function valCount(t) {
if(t[0].match(/test_user_.*/))
var testUser = t[0].match(/\d+$/);
}
Obviously there is the possibility that sometimes there will only be 1 key in the array and some times 2 or 3, so t[0] won't always be test_user_
I need to somehow pass the array to a function and perform some sort of matching, if array key starts with test_user_ then grab the value and assign it to a define variable.
Thanks guys for all your help!
You can't (reasonably) create variables with dynamic names at runtime. (It is technically possible.)
Instead, you can create object properties:
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
var obj = {};
feeds.forEach(function(entry) {
var parts = entry.split(":"); // Splits the string on the :
obj[parts[0]] = parts[1]; // Creates the property
});
Now, obj["test_user_201508_20150826080829.txt"] has the value "12345".
Live Example:
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
var obj = {};
feeds.forEach(function(entry) {
var parts = entry.split(":");
obj[parts[0]] = parts[1];
});
snippet.log(obj["test_user_201508_20150826080829.txt"]);
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>
You can do it like this, using the split function:
var i;
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
for (i = 0; i < feeds.length; i++) {
var feed = feeds[i];
console.log(feed.split(/[:]/));
}
This outputs:
["test_user_201508_20150826080829.txt", "12345"]
["test_user_list20150826", "666"]
["test_list_Summary20150826.txt", "321"]
Use the split method
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
feedMap = {}
for (i = 0; i < feeds.length; i++) {
var temp = feeds[i].split(':');
feedMap[temp[0]] = temp[1];
}
Yields:
{
"test_user_201508_20150826080829.txt":"12345",
"test_user_list20150826":"666",
"test_list_Summary20150826.txt":"321"
}
And can be accessed like:
feedMap["test_user_201508_20150826080829.txt"]
Here is a codepen
it is not very good idea but if you really need to create variables on-the-run here's the code:
for (i = 0; i < feeds.length; i++)
{
var feed = feeds[i];
window[feed.substring(0, feed.indexOf(":"))] = feed.match(/\d+$/);
}
alert(test_user_201508_20150826080829)
Of course you cannot have any variable-name-string containing banned signs (like '.')
Regards,
MichaƂ

Getting index from 2D array quickly without iteration jquery

I have this 2D array as follows:
var data = [[1349245800000, 11407.273], [1349247600000, 12651.324],
[1349249400000, 11995.017], [1349251200000, 11567.533],
[1349253000000, 11126.858], [1349254800000, 9856.455],
[1349256600000, 8901.779], [1349258400000, 8270.123],
[1349260200000, 8081.841], [1349262000000, 7976.148],
[1349263800000, 7279.652], [1349265600000, 6983.956],
[1349267400000, 7823.309], [1349269200000, 6256.398],
[1349271000000, 5487.86], [1349272800000, 5094.47],
[1349274600000, 4872.403], [1349276400000, 4168.556],
[1349278200000, 4501.939], [1349280000000, 4150.769],
[1349281800000, 4061.599], [1349283600000, 3773.741],
[1349285400000, 3876.534], [1349287200000, 3221.753],
[1349289000000, 3330.14], [1349290800000, 3147.335],
[1349292600000, 2767.582], [1349294400000, 2638.549],
[1349296200000, 2477.312], [1349298000000, 2270.975],
[1349299800000, 2207.568], [1349301600000, 1972.667],
[1349303400000, 1788.853], [1349305200000, 1723.891],
[1349307000000, 1629.002], [1349308800000, 1660.084],
[1349310600000, 1710.227], [1349312400000, 1708.039],
[1349314200000, 1683.354], [1349316000000, 2236.317],
[1349317800000, 2228.405], [1349319600000, 2756.069],
[1349321400000, 4289.437], [1349323200000, 4548.436],
[1349325000000, 5225.245], [1349326800000, 6261.156],
[1349328600000, 8103.636], [1349330400000, 10713.788]]
How do I get the index of value 1349247600000 in the array? I have tried $.inArray(1349247600000, data) but as expected this fails. Is there any other way or do I have to iterate over each? I am reluctant to add another loop to my process
This is a typical performance versus memory issue. The only way (that I know of) to avoid looping through the array, would be to maintain a second data structure mapping the timestamps to the index of the array (or whatever data might needed).
So you would have
var data = [
[1349245800000, 11407.273],
[1349247600000, 12651.324],
// ...
[1349330400000, 10713.788]
];
// the timestamps pointing at their respective indices
var map = {
'1349245800000': 0, // 0
'1349247600000': 1, // 1
// ...
'1349330400000': 42, // n - 1 (the length of the data array minus one)
}
This way, you use more memory, but have a constant lookup time when needing the index of the item in the array that a given timestamp belongs to.
To get the index of a given timestamp do:
map['1349247600000']; // resulting in 1 (e.g.)
If the data structure is dynamically changed, you would of course need to maintain the map data structure, but depending on the context in which you need the lookup, the constant time lookup can potentially be a real time saver compared to a linear time lookup.
I think you need a different data structure.
Try using a standard javascript object ({ key: value } - sometimes called a map or dictionary) to express your data. Looking up keys in an object is highly optimized (using something called hash tables).
If the index in your array has any meaning, store it as a property (typically named _id).
Ideally you should be using an object for this:
var data = {
'1349247600000': 12651.324
}
which you can access like:
data['1349247600000'];
However, this might be a nice solution (IE9 and above) in the meantime:
var search = 1349247600000;
function findIndex(data, search) {
var filter = data.filter(function (el, i) {
el.unshift(i);
return el[1] === search;
});
return filter[0][0];
}
console.log(findIndex(data, search));
fiddle : http://jsfiddle.net/CLa56/
var searchElement = 1349251200000;
var strdata = data.toString();
var newdata = eval("[" + strdata + "]");
var indexsearch = newdata.indexOf(searchElement);
var index = indexsearch/2; // 2 because array.length = 2
var params = {id: 1349251200000, index: -1};
data.some(function (e, i) {
if (e[0] === this.id) {
this.index = i;
return true;
}
}, params);
console.log(params.index);
jsfiddle
MDN|some Array Method
Note that this solution stops iterating after found, not necessarily over the entire array, so could be much faster for large arrays.
What about a custom cross browser solution ?
function findIndexBy(a, fn) {
var i = 0, l = a.length;
for (; i < l; i++) {
if (fn(a[i], i)) {
return i;
}
}
return -1;
}
Usage :
var list = [[1],[2],[3]], idx;
// idx === 1
idx = findIndexBy(list, function (item, i) {
return item[0] === 2;
});
// idx === -1
idx = findIndexBy(list, function (item, i) {
return item[0] === 4;
});

Modify a global variable based on an object property

I'm trying to learn object oriented javascript and ran into the following problem:
I have an object constructor (is that the right term?) like this:
function itemCreator(itemName, itemType, itemPositionX, itemPositionY) {
this.itemName = itemName;
this.itemType = itemType;
this.itemPositionX = itemPositionX;
this.itemPositionY = itemPositionY;
allItems.push(this); //store all items in a global variable
}//end itemCreator;
//then I use it to create an object
megaRocket = new itemCreator (
'megarocket',
'item_megarocket',
108,
475
)
Now I realised I also need to map these objects to modify different global variables based on which "itemType" the object has. This is where I am stuck. How can I make a global variable that only objects with a specific itemType property can modify?
For example I would like to create an object that increments a variable called amountOfMegarockets, but only if the itemType for that object is "item_megarocket".
I later plan on looping an array of these items to see if player object touches them (to collect the item):
function checkForItems(){
var itemLen =allItems.length;
for (i=0; i < itemLen; i++){
var itemObject = allItems[i];
if ( //checking for "collisions" here
(ship.x < (itemObject.itemBitmap.x + itemObject.size) && (ship.x + shipWidth) > itemObject.itemBitmap.x) &&
(ship.y < (itemObject.itemBitmap.y + itemObject.size) && (ship.y + shipWidth) > itemObject.itemBitmap.y)
){
itemObject.actor.y = -500; //just removing the item from canvas here (temporary solution)
// Here comes pseudo code for the part that I'm stuck with
variableBasedOnItemObject.itemType++;
}
I hope my explanation makes sense to someone!
EDIT:
Bergi's answer makes most sense to me, but I can't get the syntax right. Here's how I'm trying to use Bergi's code:
var amounts = {},
allItems = [];
function itemCreator(itemName, itemType, itemPositionX, itemPositionY) {
this.itemName = itemName;
this.itemType = itemType;
this.itemPositionX = itemPositionX;
this.itemPositionY = itemPositionY;
(amounts[itemType]=2); // this is different from bergi's example because I need to set the initial value of the item to two
//I also shouldn't increase the item amount on creation of the item, but only when it's specifically called from another function
this.increaseCount = amounts[itemType]++; //this should IMO increase the itemType amount inside the amounts object when called, but it doesn't seem to work
}
//creating the object the way bergi suggested:
allItems.push(new itemCreator('shootUp001', 'item_up', 108, 475));
Now here's the problematic part:
function checkForItems(){
var itemLen =allItems.length;
for (i=0; i < itemLen; i++){
var itemObject = allItems[i];
if ( my condition here)
){
//code below is not increasing the value for the current itemType in the amounts object.
//Probably a simple syntax mistake?
itemObject.itemType.increaseCount;
}
}
}
Why is my call of itemObject.itemType.increaseCount; not increasing the value of amounts.itemType?
Increment a global variable called amountOfMegarockets, but only if the itemType for that object is "item_megarocket".
Don't use a global variable for each of those item types. Do use one object (in global or local scope) which counts the amouts of each type on its properties.
var amounts = {},
allItems = [];
function Item(itemName, itemType, itemPositionX, itemPositionY) {
this.itemName = itemName;
this.itemType = itemType;
this.itemPositionX = itemPositionX;
this.itemPositionY = itemPositionY;
amounts[itemType]++ || (amounts[itemType]=1); // count by type
allItems.push(this); // store all items
}
Notice that I wouldn't put all Item instances in an array by default, better omit that line and let it do the caller:
allItems.push(new Item('megarocket', 'item_megarocket', 108, 475));
you can do some things like
(function (global) {
// create a scope
var allItems = [];
global.itemCreator = function(itemName, itemType, itemPositionX, itemPositionY) {
this.itemName = itemName;
this.itemType = itemType;
this.itemPositionX = itemPositionX;
this.itemPositionY = itemPositionY;
allItems.push(this); //store all items in a global variable
}//end itemCreator;
})(this);
this will work. but seriously dont complicate too mutch your code juste to make private var. if someone want to cheat using debugger he will always found a way to do it.
---- edit
If you juste want access to global var base on itemType you can do some thing like:
function checkForItems(){
var itemLen =allItems.length;
for (i=0; i < itemLen; i++){
var itemObject = allItems[i];
if ( //checking for "collisions" here
(ship.x < (itemObject.itemBitmap.x + itemObject.size) && (ship.x + shipWidth) > itemObject.itemBitmap.x) &&
(ship.y < (itemObject.itemBitmap.y + itemObject.size) && (ship.y + shipWidth) > itemObject.itemBitmap.y)
){
itemObject.actor.y = -500; //just removing the item from canvas here (temporary solution)
// Here comes pseudo code for the part that I'm stuck with
if (window[itemObject.itemType + "Data"])) {
variableBasedOnItemObject.itemType++;
} else {
window[itemObject.itemType + "Data"] = {
itemType: 1
}
}
}
}
}

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