JS array string patch name to array(object) - javascript

i have trouble with js array.
I have patch name(string) look like ( "user.joey.friends.0.franc" ) and i need to "compress" to look like this:
console.log( parseArray( "user.joey.friends.0.franc" ) );
//Object {
user: {
joey: {
friends: {
0: {
franc: 1
}
}
}
}
}
Any ideas, how to do that ?


Here's a non recursive way to get you most of the way there.
function compress(str) {
var split = str.split('.'), obj = {}, current = obj, i;
for (i = 0; i < split.length; i++){
current[split[i]] = {} ;
current = current[split[i]];
}
return obj;
}


If you're saying you have an object with the structure you've quoted, and you're trying to look up the property defined by your string "user.joey.friends.0.franc", that's a fairly straightforward loop: Live Example
function findProperty(obj, path) {
var steps = path.split(/\./);
var step;
var n;
for (n = 0; n < steps.length; ++n) {
step = steps[n];
if (!(step in obj)) {
return undefined;
}
obj = obj[step];
}
return obj;
}
var a = {
user: {
joey: {
friends: {
0: {
franc: 1
}
}
}
}
};
console.log(findProperty(a, "user.joey.friends.0.franc")); // "1"


If you're trying to create an object from a string, this solution is what I currently use until I find something better (I believe it based on a namespacing method from Yahoo):
function createObject() {
var a = arguments, i, j, d, _this;
var out = {};
for (i = 0; i < a.length; i = i + 1) {
d = a[i].split('.');
out2 = out;
for (j = 0; j < d.length; j = j + 1) {
out2[d[j]] = out2[d[j]] || {};
out2 = out2[d[j]];
}
}
return out;
}
createObject('user.joey.friends.0.franc');
DEMO

Related

How do I build an object counting occurrences in an Array in JavaScript?

I want to count how often a number in an Array occurs. For example, in Python I can use Collections.Counter to create a dictionary of how frequently an item occurs in a list.
This is as far as I've gotten in JavaScript:
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
/* obj[array[i]] = +=1 */ <= pseudo code
}
How can I create this frequency counter object?

Close but you can't increment undefined so you need to set initial value if it doesn't exist
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
obj[array[i]] = (obj[array[i]] || 0) +1 ;
}

You were almost there. See below code:
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
obj[array[i]] = (obj[array[i]] || 0 ) +1;
}
console.log(obj);

Create an object and check if that specific key exist.If exist then increase it's value by 1
var array = [1, 4, 4, 5, 5, 7];
var obj = {};
for (var i = 0; i < array.length; i++) {
if (obj.hasOwnProperty(array[i])) {
obj[array[i]] += 1;
} else {
obj[array[i]] = 1;
}
}
console.log(obj)

You can use the ? : ternary operator to set initial value as 1 and then increment it on subsequent matches.
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
obj[array[i]] = obj[array[i]]?obj[array[i]]+1:1;
}
console.log(obj);

If the array is always going to be same, and you are going to check frequency of multiple items in the same array without it it being modified, #JohanP's answer is good.
But if you are only going to check frequency of only one item, or the array can change, creating the object is nothing but extra overhead.
In that case, you can do something like this:
const getItemFrequency = function(array, item) {
return array.filter(i => i === item).length;
}
var array = [1,4,4,5,5,7];
console.log(getItemFrequency(array, 4));

Concise logic written as proper function:
function countArrayItemFrequecy(array) {
const length = array.length;
const map = {};
for ( let i = 0; i < length; i++ ) {
let currentItem = array[i];
if (typeof map[currentItem] !== 'undefined' ) {
map[currentItem]++
} else {
map[currentItem] = 1
}
}
return map;
}

You need to make sure to assign default value to your frequency object for the first occurrence of the item. As a shortcut you can use ternary operator
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
obj[array[i]] = obj[array[i]] ? obj[array[i]]++ : 1;
}
which is the same as:
var array = [1,4,4,5,5,7];
var obj = {};
for (var i=0; i < array.length; i++) {
if (obj[array[i]]) {
obj[array[i]]++;
} else {
obj[array[i]] = 1;
}
}

You can use Object.assign: below clones map and then increments/adds the counter. These are pure (no side effects/param reassignment), single-purpose functions.
addToMap does the same thing as { ...map, map[e]: [e]: (map[e] || 0) + 1 }, but that requires babel.
const addToMap = (map, e) => Object.assign({}, map, { [e]: (map[e] || 0) + 1 });
const buildMap = a => a.reduce(addToMap, {});

Using Array.reduce:
arr.reduce(function (acc, item) {
acc[item] = (acc[item] || 0) + 1;
return acc;
}, {});
Example:
var arr = [1,1,2,4,1,4];
var counts = arr.reduce(function (acc, item) {
acc[item] = (acc[item] || 0) + 1;
return acc;
}, {});
console.log(counts);

javascript array - increment value at given key

I have a dynamic array and I am trying to increment the value by 1 if the key exists in the array. According to my debug it is incrementing the key and and creating a second key/value pair.
A snippet of my code:
for (var i = 0; i < choices.length; i++) {
console.log(choices[i]);
if (choices[i].YearTermId == 1) {
if (!lookup(firstChoice, choices[i].FirstChoiceOptionId)) {
firstChoice.push({
key: choices[i].FirstChoiceOptionId,
value: 1
});
} else {
firstChoice[choices[i].FirstChoiceOptionId] = firstChoice[choices[i].FirstChoiceOptionId] + 1;
}
more if/else..
function lookup( arr, name ) {
for(var i = 0, len = arr.length; i < len; i++) {
if( arr[ i ].key === name )
return true;
}
return false;
}

You're using an array where you should be using an object. If you use an object, your code can be rewritten as:
var firstChoice = {};
for (var i = 0; i < choices.length; i++) {
var firstChoiceOptionId = choices[i].FirstChoiceOptionId;
if (choices[i].YearTermId == 1) {
firstChoice[firstChoiceOptionId] = firstChoice[firstChoiceOptionId]
? firstChoice[firstChoiceOptionId] + 1
: 1;
/* ... */
}
}
If you need the data as an array afterwards, just map it:
var firstChoiceArray = Object.keys(firstChoice).map(function(key) {
return {
key: key,
value: firstChoice[key]
};
});
Conversely, if you have an input array and want to convert it to an object for manipulation, reduce it:
var firstChoice = firstChoiceArray.reduce(function(result, current) {
result[current.key] = current.value;
return result;
}, {});

I think you should increment value key, like:
firstChoice[choices[i].FirstChoiceOptionId].value ++;
And I would like to rewrite this code to:
var firstChoice = {};
for (var i = 0; i < choices.length; i++) {
if (choices[i].YearTermId == 1) {
if (!firstChoice[choices[i].FirstChoiceOptionId]) {
firstChoice[choices[i].FirstChoiceOptionId] = 0;
}
firstChoice[choices[i].FirstChoiceOptionId]++;
}
}
console.log(firstChoice);

Try with Array.map:
Example:
var a = [{key:"ab","value":1},{key:"cd","value":1},{key:"ef","value":1}];
a.map(function(item){if(item.key == this){item.value++}}, "cd");
So, a[1] will have value 2 after that.

Check for repeated characters in a string Javascript

I was wondering if there is a way to check for repeated characters in a string without using double loop. Can this be done with recursion?
An example of the code using double loop (return true or false based on if there are repeated characters in a string):
var charRepeats = function(str) {
for(var i = 0; i <= str.length; i++) {
for(var j = i+1; j <= str.length; j++) {
if(str[j] == str[i]) {
return false;
}
}
}
return true;
}
Many thanks in advance!

This will do:
function hasRepeats (str) {
return /(.).*\1/.test(str);
}

(A recursive solution can be found at the end of this answer)
You could simply use the builtin javascript Array functions some MDN some reference
var text = "test".split("");
text.some(function(v,i,a){
return a.lastIndexOf(v)!=i;
});
callback parameters:
v ... current value of the iteration
i ... current index of the iteration
a ... array being iterated
.split("") create an array from a string
.some(function(v,i,a){ ... }) goes through an array until the function returns true, and ends than right away. (it doesn't loop through the whole array, which is good for performance)
Details to the some function here in the documentation
Here some tests, with several different strings:
var texts = ["test", "rest", "why", "puss"];
for(var idx in texts){
var text = texts[idx].split("");
document.write(text + " -> " + text.some(function(v,i,a){return a.lastIndexOf(v)!=i;}) +"<br/>");
}
//tested on win7 in chrome 46+
If you will want recursion.
Update for recursion:
//recursive function
function checkString(text,index){
if((text.length - index)==0 ){ //stop condition
return false;
}else{
return checkString(text,index + 1)
|| text.substr(0, index).indexOf(text[index])!=-1;
}
}
// example Data to test
var texts = ["test", "rest", "why", "puss"];
for(var idx in texts){
var txt = texts[idx];
document.write( txt + " ->" + checkString(txt,0) + "<br/>");
}
//tested on win7 in chrome 46+

you can use .indexOf() and .lastIndexOf() to determine if an index is repeated. Meaning, if the first occurrence of the character is also the last occurrence, then you know it doesn't repeat. If not true, then it does repeat.
var example = 'hello';
var charRepeats = function(str) {
for (var i=0; i<str.length; i++) {
if ( str.indexOf(str[i]) !== str.lastIndexOf(str[i]) ) {
return false; // repeats
}
}
return true;
}
console.log( charRepeats(example) ); // 'false', because when it hits 'l', the indexOf and lastIndexOf are not the same.

function chkRepeat(word) {
var wordLower = word.toLowerCase();
var wordSet = new Set(wordLower);
var lenWord = wordLower.length;
var lenWordSet =wordSet.size;
if (lenWord === lenWordSet) {
return "false"
} else {
return'true'
}
}

Using regex to solve=>
function isIsogram(str){
return !/(\w).*\1/i.test(str);
}
console.log(isIsogram("isogram"), true );
console.log(isIsogram("aba"), false, "same chars may not be adjacent" );
console.log(isIsogram("moOse"), false, "same chars may not be same case" );
console.log(isIsogram("isIsogram"), false );
console.log(isIsogram(""), true, "an empty string is a valid isogram" );

The algorithm presented has a complexity of (1 + n - (1)) + (1 + n - (2)) + (1 + n - (3)) + ... + (1 + n - (n-1)) = (n-1)*(1 + n) - (n)(n-1)/2 = (n^2 + n - 2)/2 which is O(n2).
So it would be better to use an object to map and remember the characters to check for uniqueness or duplicates. Assuming a maximum data size for each character, this process will be an O(n) algorithm.
function charUnique(s) {
var r = {}, i, x;
for (i=0; i<s.length; i++) {
x = s[i];
if (r[x])
return false;
r[x] = true;
}
return true;
}
On a tiny test case, the function indeed runs a few times faster.
Note that JavaScript strings are defined as sequences of 16-bit unsigned integer values. http://bclary.com/2004/11/07/#a-4.3.16
Hence, we can still implement the same basic algorithm but using a much quicker array lookup rather than an object lookup. The result is approximately 100 times faster now.
var charRepeats = function(str) {
for (var i = 0; i <= str.length; i++) {
for (var j = i + 1; j <= str.length; j++) {
if (str[j] == str[i]) {
return false;
}
}
}
return true;
}
function charUnique(s) {
var r = {},
i, x;
for (i = 0; i < s.length; i++) {
x = s[i];
if (r[x])
return false;
r[x] = true;
}
return true;
}
function charUnique2(s) {
var r = {},
i, x;
for (i = s.length - 1; i > -1; i--) {
x = s[i];
if (r[x])
return false;
r[x] = true;
}
return true;
}
function charCodeUnique(s) {
var r = [],
i, x;
for (i = s.length - 1; i > -1; i--) {
x = s.charCodeAt(i);
if (r[x])
return false;
r[x] = true;
}
return true;
}
function regExpWay(s) {
return /(.).*\1/.test(s);
}
function timer(f) {
var i;
var t0;
var string = [];
for (i = 32; i < 127; i++)
string[string.length] = String.fromCharCode(i);
string = string.join('');
t0 = new Date();
for (i = 0; i < 10000; i++)
f(string);
return (new Date()) - t0;
}
document.write('O(n^2) = ',
timer(charRepeats), ';<br>O(n) = ',
timer(charUnique), ';<br>optimized O(n) = ',
timer(charUnique2), ';<br>more optimized O(n) = ',
timer(charCodeUnique), ';<br>regular expression way = ',
timer(regExpWay));

let myString = "Haammmzzzaaa";
myString = myString
.split("")
.filter((item, index, array) => array.indexOf(item) === index)
.join("");
console.log(myString); // "Hamza"

Another way of doing it using lodash
var _ = require("lodash");
var inputString = "HelLoo world!"
var checkRepeatition = function(inputString) {
let unique = _.uniq(inputString).join('');
if(inputString.length !== unique.length) {
return true; //duplicate characters present!
}
return false;
};
console.log(checkRepeatition(inputString.toLowerCase()));

const str = "afewreociwddwjej";
const repeatedChar=(str)=>{
const result = [];
const strArr = str.toLowerCase().split("").sort().join("").match(/(.)\1+/g);
if (strArr != null) {
strArr.forEach((elem) => {
result.push(elem[0]);
});
}
return result;
}
console.log(...repeatedChar(str));
You can also use the following code to find the repeated character in a string

//Finds character which are repeating in a string
var sample = "success";
function repeatFinder(str) {
let repeat="";
for (let i = 0; i < str.length; i++) {
for (let j = i + 1; j < str.length; j++) {
if (str.charAt(i) == str.charAt(j) && repeat.indexOf(str.charAt(j)) == -1) {
repeat += str.charAt(i);
}
}
}
return repeat;
}
console.log(repeatFinder(sample)); //output: sc

const checkRepeats = (str: string) => {
const arr = str.split('')
const obj: any = {}
for (let i = 0; i < arr.length; i++) {
if (obj[arr[i]]) {
return true
}
obj[arr[i]] = true
}
return false
}
console.log(checkRepeats('abcdea'))

function repeat(str){
let h =new Set()
for(let i=0;i<str.length-1;i++){
let a=str[i]
if(h.has(a)){
console.log(a)
}else{
h.add(a)
}
}
return 0
}
let str = '
function repeat(str){
let h =new Set()
for(let i=0;i<str.length-1;i++){
let a=str[i]
if(h.has(a)){
console.log(a)
}else{
h.add(a)
}
}
return 0
}
let str = 'haiiiiiiiiii'
console.log(repeat(str))
'
console.log(repeat(str))

Cleanest way for me:
Convert the string to an array
Make a set from the array
Compare the length of the set and the array
Example function:
function checkDuplicates(str) {
const strArray = str.split('');
if (strArray.length !== new Set(strArray).size) {
return true;
}
return false;
}

You can use "Set object"!
The Set object lets you store unique values of any type, whether
primitive values or object references. It has some methods to add or to check if a property exist in the object.
Read more about Sets at MDN
Here how i use it:
function isIsogram(str){
let obj = new Set();
for(let i = 0; i < str.length; i++){
if(obj.has(str[i])){
return false
}else{
obj.add(str[i])
}
}
return true
}
isIsogram("Dermatoglyphics") // true
isIsogram("aba")// false

JavaScript stable sort issue

I've looked around for some help on this topic but was unable to find some help or guidance.
My problem is I am attempting to perform a sort on a series of values separated by an equals sign.
"Foo=Bar , Shenanigans=Fun, A=B ...etc"
My current sort works, but only if no value is the same. If I have some values like:
"Foo=Bar, A=Bar, Potato=Bar"
When the sort is complete they will all be "A=Bar"
My current sort looks like this, would someone be able to point me in the right direction?
$('#sortByValue').click(function() {
var textValueArray = document.getElementById('nameValuePairList');
textArray = new Array();
valueArray = new Array();
oldValues = new Array();
for (i = 0; i < textValueArray.length; i++) {
valueArray[i] = textValueArray.options[i].value;
textArray[i] = textValueArray.options[i].text;
oldValues[i] = textValueArray.options[i].value;
}
valueArray.sort(function(a, b) {
return a.toLowerCase().localeCompare(b.toLowerCase());
});
for (i = 0; i < textValueArray.length; i++) {
textValueArray.options[i].value = valueArray[i];
for (j = 0; j < textValueArray.length; j++) {
if (valueArray[i] == oldValues[j]) {
textValueArray.options[i].text = textArray[j];
j = textValueArray.length;
}
}
}
});
I know that my problem lies here: valueArray[i] == oldValues[j]
as when the data comes in valueArray = {Bar, Foo, Bar} while textArray = {Foo=Bar, A=Foo, Test=Bar}
However, I am unsure how to best resolve it.

Sort textArray directly, don't use valueArray since it will contain duplicates:
textArray.sort(function(a,b){
var aa = a.split('=')
var bb = b.split('=')
var a_key = aa[0].toLowerCase(), a_val = aa[1].toLowerCase();
var b_key = bb[0].toLowerCase(), b_val = bb[1].toLowerCase();
if (a_val == b_val) return a_key.localeCompare(b_key);
return a_val.localeCompare(b_val);
})

I would do something like this:
document.getElementById('sortByName').onclick = sortByName;
function sortByName(){
var myList = document.getElementById('list');
var values = [];
for (var i=0;i<myList.options.length;i++) {
values[i] = myList.options[i].text;
}
values.sort(function (a, b){
if(a !== "" && b !== ""){
return a.split('=')[0].localeCompare(b.split('=')[0]);
} else {
return 0;
}
});
clearList(myList);
fillList(myList, values);
}
function clearList(list) {
while (list.options.length > 0) {
list.options[0] = null;
}
}
function fillList(myList, values){
for (var i=0;i<values.length;i++) {
var option = document.createElement("option");
option.text = values[i];
myList.options[i] = option;
}
}
Take a look at this demo

The reasoning behind doing this at all will have you wondering why, in the future. I think you want something like this:
function inArray(v, a){
for(var i=0,l=a.length; i<l; i++){
if(a[i] === v){
return true;
}
}
return false;
}
function sortWeirdString(str){
var pairs = str.split(/\s?,\s?/), n = [], v = [], c = [], ci, idx = [], cl, nv = [], ra = [];
for(var i=0,l=pairs.length; i<l; i++){
var pair = pairs[i].split(/\s?=\s?/);
n.push(pair[0]); v.push(pair[1]);
}
c = n.concat().sort(); cl = c.length
for(var i=0; i<cl; i++){
var cv = c[i];
if(n.indexOf){
ci = n.indexOf(cv);
if(inArray(ci, idx)){
ci = n.indexOf(cv, ci+1);
}
idx.push(ci);
}
else{
for(var x=0; x<cl; x++){
if(n[x] === cv){
if(inArray(x, idx)){
continue;
}
idx.push(x);
}
}
}
}
for(var i=0,l=idx.length; i<l; i++){
ra.push(c[i]+'='+v[idx[i]]);
}
return ra.join(', ');
}
$('#sortByValue').click(function(){
console.log(sortWeirdString($('#nameValuePairList').val()));
}

Update 2019
The spec has changed and #Array.prototype.sort is now a stable sort.
The elements of this array are sorted. The sort must be stable (that
is, elements that compare equal must remain in their original order)
This is already implemented in V8

Knowing position of a value under twodimensional Array

I have a SummaryData array as shown
var summaryData = [[0,100.34],[1,102.31],[2,131.08],[3,147.94],[4,172.55],[5,181.05],[6,180.08]];
My question is:
Is it possible to find out what the position of a value is?
(For example, how can I know where 147.94 is?) (I am expecting "3")

Update:
A more prototype-y way:
var result = summaryData.detect(function(item) { return item[1] === 147.94; });
alert(result[0]);
Or:
function getKey(arr, value) {
var key = null,
item;
for (var i = 0; i < arr.length && !key; i++) {
item = arr[i];
if (item[1] === value) {
key = i;
}
}
return key;
}
Usage:
var n = getKey(summaryData, 147.94); // returns 3.

At the risk of doing your homework for you...
var summaryData = [[0,100.34],[1,102.31],[2,131.08],[3,147.94],[4,172.55],[5,181.05],[6,180.08]];
function findPosition(value, dataArray) {
var a;
for (var i=0, iLen=dataArray.length; i<iLen; i++) {
a = dataArray[i];
for (var j=0, jLen=a.length; j<jLen; j++){
if (value == a[j]) {
return i + ',' + j;
}
}
}
}
alert(findPosition(131.08, summaryData)); // 2,1
The above returns the position of the first match.
Edit
I see now that you don't need to iterate over the second array, just look at the second value, so:
function findPosition(value, dataArray) {
var a;
for (var i=0, iLen=dataArray.length; i<iLen; i++) {
a = dataArray[i];
if (value == a[1]) {
return a[0];
}
}
}
alert(findPosition(131.08, summaryData)); //2
Or if the data format is always as specified and there may be thousands of values, then it may be much faster to do:
function findPosition(value, dataArray) {
var re = new RegExp('[^,],' + value);
var m = dataArray.join().match(re);
return m && m[0].replace(/,.*/,'');
// Or
// return m && m[0].split(',')[0];
}

function getPosition(candidate) {
var i = summaryData.length;
while (i) {
i -= 1;
if (summaryData[i][1] === candidate) {
return summaryData[i][0];
}
}
}

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