function createTextFields(obj) {
for (var i = 0; i < obj.length; i++) {
var dataDump = {};
for (var key in obj[i]) {
var textField = Ti.UI.createTextField(pm.combine($$.labelBrown, {
left: 200,
height:35,
value:obj[i][key],
width:550,
keyboardType:Ti.UI.KEYBOARD_NUMBER_PAD,
layout:'horizontal',
backgroundColor:'transparent',
id:i
}));
dataDump[key] = textField.value;
var callback = function (vbKey) {
return function (e) {
dataDump[vbKey] = e.source.value;
};
}(key);
}
globalData.push(dataDump);
}
}
I am using the simlar code for Adding the data and it works fine. I posted the problem yesterday and it got resolved...
Last Object is always getting updated?
Now when i go to edit page, it shows me four text fields or number of text fields added... now when i edit something and click on save... the value get's updated on the fourth or the last TextFields Object...
Don't define functions inside loops. Computationally expensive and leads to problems, like this one. Here's a fix that should solve it:
function createTextFields(obj) {
var callback = function (vbKey, localDump) {
return function (e) {
localDump[vbKey] = e.source.value;
};
}
var i;
var max = obj.length;
for (i = 0; i < max; i++) {
var dataDump = {};
for (var key in obj[i]) {
dataDump[key] = textField.value;
var callBackInstance = function(keyn, dataDump);
}
globalData.push(dataDump);
}
}
JavaScript does not have block level scope, so your variables dataDump and callback, though "declared" inside for-loops actually belong to the function. As in, you're saving a value to dataDump, then you're overwriting it, each time you go through the loop. Which is why finally only the code that operated on the last value remains.
Take a look at What is the scope of variables in JavaScript? too.
Related
First take a look at my simple codes below:
function mySecondFunction(objArray,setFunc)
{
for (let i = 0; i < objArray.length; i++)
{
objArray[i].info.setTop(72);
}
}
function myFunction()
{
let myObjArray = [];
for (let i = 0; i < 10; i++)
{
myObjArray.push({
info:{topVar:0,
bottomVar:0,
get top() {return this.topVar;},
get bottom() {return this.bottomVar;},
setTop: function(input) {this.topVar = input;},
setBottom: function(input) {this.bottomVar = input; }
}
});
}
mySecondFunction(myObjArray); // This works Fine
mySecondFunction(myObjArray,setTop); // I want something like this!!!
}
As you can see, I want to pass a method of an object to another function. I know a lot of possible solutions to avoid this, but I want to know whether it is possible or not.
Detach it and pass as an argument. Remember to use call to set the intended this value.
function mySecondFunction(objArray, setFunc)
{
for (let i = 0; i < objArray.length; i++)
{
setFunc.call(objArray[i].info, 72);
/* explicitly telling that:
please set 'this' value in this function to be 'objArray[i].info' when running,
allowing, e.g. `this.topVar` in
`setTop: function(input) {this.topVar = input;}`
to be operating on `objArray[i].info.topVar` */
}
}
function myFunction()
{
let myObjArray = [];
for (let i = 0; i < 10; i++)
{
myObjArray.push({
info:{topVar:0,
bottomVar:0,
get top() {return this.topVar;},
get bottom() {return this.bottomVar;},
setTop: function(input) {this.topVar = input;},
setBottom: function(input) {this.bottomVar = input; }
}
});
}
mySecondFunction(myObjArray, myObjArray[0].info.setTop);
/* once detaching the method from the object,
(if we are not using arrow functions),
we lose 'this' value, meaning we are losing
the target of object that we want to operate on */
console.log(myObjArray)
}
myFunction();
You can target item number in the array list. You can do statically (i.e. 1-???) or dynamically with an iteration and a variable. You can then the object property within that. For example:
myObjArray[0].info.setTop
That will target the 1st item in the array. Be sure to omit parentheses (()) when passing the method as you want to pass the function reference not the result
I need to copy a string inside an array to a value inside another array that is created in a loop. In the end when I print all names are the last in the array of names. I want to copy/clone the value so that I don't have a reference and I would like it to be only in native javascript without external libraries.
This is my code
var exp_names =["name1","name2","name3"];
var i;
for (i = 0; i < exp_names.length; i++) {
d3.tsv("data/"+exp_names[i], function(data) {
data.forEach(function(d){
//Do stuff with my tsv
d.expId = exp_names[i];
});
});
});
And then all expId are "name3"
Data is loading correctly per file.
I have tried with jquery's extend function and also lodash's clone function, I have tried my own clone function and nothing works it will still throw "name3" for all the expId.
These didn't work:
var newname = new String(exp_names[i]);
var newname = $.extend(true, {}, exp_names[i]);
var newname = $.extend( {}, exp_names[i]);
var newname = _.clone(exp_names[i]);
var newname = exp_names[i].slice(0);
I am desperate by now.
You need to use bind function.
var exp_names =["name1","name2","name3"];
var i;
var func = [];
for (i = 0; i < exp_names.length; i++) {
func[i]=(function(index){
d3.tsv("data/"+exp_names[index], function(data) {
data.forEach(function(d){
//Do stuff with my tsv
d.expId = exp_names[index];
});
});
}).bind(this,i);
}
for(i = 0; i < 3; i++){
func[i](i);
}
Another solution is to use let keyword.
ES6 provides the let keyword for this exact circumstance. Instead of using closures, we can just use let to set a loop scope variable.
Please try this:
for (let i = 0; i < exp_names.length; i++) {
d3.tsv("data/"+exp_names[i], function(data) {
data.forEach(function(d){
//Do stuff with my tsv
d.expId = exp_names[i];
});
});
}
I guess usage of IIFE and bind together, in the first answer is a little weird. It's best to choose either one of them. Since in the newest versions of the browsers bind is way faster than an IIFE closure and the let keyword I might suggest you the bind way.
A similar example to your case might be as folows;
var exp_names = ["name1","name2","name3"],
lib = {doStg: function(d,cb){
cb(d);
}
},
data = [{a:1},{a:2},{a:3}];
for (i = 0; i < exp_names.length; i++) {
lib.doStg(data, function(i,d) {
d.forEach(function(e){
//Do stuff with doStg
e.expId = exp_names[i];
console.log(e);
});
}.bind(null,i));
}
I thought making a simple function where if you click on a button a number will show up inside of a paragraph. And if you continue to click on the button the number inside the paragraph tag will increase. However, I'm getting an error message saying that getElementsByTagName is not a function. Here is the code on jsfiddle, I know there is something simple that I'm doing wrong but I don't know what it is.
HTML
<div class="resist" id="ex1"><h2>Sleep</h2><p></p><button>Resist</button></div>
<div class="resist" id="ex2"><h2>Eat</h2><p></p><button>Resist</button></div>
Javascript
var count = 0;
var resist = document.getElementsByClassName('resist') ;
for(var i = 0; i < resist.length; i++)
{ var a = resist[i];
a.querySelector('button').addEventListener('click', function(a){
count +=1;
a.getElementsByTagName('p')[0].innerHTML = count;
});
}
You are overwriting a variable with event object passed into event handler. Change the name to e maybe, or remove it altogether as you are not using it anyway:
a.querySelector('button').addEventListener('click', function(e /* <--- this guy */) {
count += 1;
a.getElementsByTagName('p')[0].innerHTML = count;
});
Another problem you are going to have is classical closure-in-loop issue. One of the solutions would be to use Array.prototype.forEach instead of for loop:
var count = 0;
var resist = Array.prototype.slice.call(document.getElementsByClassName('resist'));
// ES6: var resist = Array.from(document.getElementsByClassName('resist'));
resist.forEach(function(a) {
a.querySelector('button').addEventListener('click', function(e) {
count += 1;
a.getElementsByTagName('p')[0].innerHTML = count;
});
});
vars in Javascript are function scoped, so you must wrap your event listener binding in a closure function to ensure the variable you're trying to update is correctly set.
(Note: I've renamed a to div in the outer function and removed the arg from the inner click function).
var count = 0;
var resist = document.getElementsByClassName('resist') ;
var div;
for(var i = 0; i < resist.length; i++)
{
div = resist[i];
(function(div){
div.querySelector('button').addEventListener('click', function(){
count +=1;
div.getElementsByTagName('p')[0].innerHTML = count;
});
})(div);
}
This may seem like a duplicate question, and to some extent, it is, but I have already been through many similar questions, and sadly, none have suited my need. I would really appreciate problem-specific advice.
My main problem in the JavaScript code here is that I cannot access the values in the variables RememberText20 and RememberFullText, in function TextLimiter, from function ReadMoreLessText. The "Message" is an argument for the ReadMoreLessText function, which essentially matches the element clicked to the correct value in the aforementioned variables, which are themselves arrays.
*I know there is nothing wrong with the arrays themselves, as they retain their values as they are supposed to, because a simple alert() proves this. Similarly, there is nothing wrong with the Message argument, as the function ReadMoreLessText works fine with other values.
My simple problem is that I cannot access the values in the aforementioned variables, from the ReadMoreLessText function, although they are global variables, as they should be.
I would really appreciate a problem-specific answer here. Thank you in advance.
// JavaScript Document
//Start Text250
window.onload = function TextLimiter() {
for (y = 0; y < 6; y++) {
FullText = document.getElementsByClassName("Introduction")[y].innerHTML;
TextLength = FullText.length;
RememberFullText = [];
RememberFullText[y] = FullText;
var Text250 = FullText.substr(0, 250) + "...";
RememberText250 = [];
RememberText250[y] = Text250;
if (TextLength > 250) {
document.getElementsByClassName("Read_More")[y].innerHTML = "Read More→";
document.getElementsByClassName("Introduction")[y].innerHTML = Text250;
} else {
document.getElementsByClassName("Read_More")[y].innerHTML = "";
}
}
};
//End Text250
//Start ReadMoreLessText
var ReadMore = function(Message) {
var ScreenText = document.getElementsByClassName("Introduction")[Message].innerHTML;
if (ScreenText === RememberText250[Message]) {
document.getElementsByClassName("Introduction")[Message].innerHTML = RememberText250[Message];
} else {
document.getElementsByClassName("Introduction")[Message].innerHTML = RememberText250[Message];
}
};
//End ReadMoreLessText
Try defining RememberFullText and RememberText250 outside the enclosing for loop.
window.onload = function TextLimiter() {
RememberFullText = [];
RememberText250 = []
for (y = 0; y < 6; y++) {
...
As written they are set to an empty array in each iteration of the loop. Hence only the last entry of each array will be retained after the loop has finished.
I don't see your variables declared as globals. Do you have a var RememberText20, RememberFullText; outside any function?
Background
I have a plain JS array, initially empty. I later populate it with values. The values sent to it are numbers that are Knockout observables. Later, I want to compare those values to values in another, knockout observable array. My problem is that whenever I pass the index of the current item in my array loop, and pass that index value (a number!), the array returns a function. To get an idea, look at the JS that follows.
Note that my project and actual script is viewable on JSBin. Further, to view the problem in the console, you have to add assignments, then press 'sort'.
JSBin: http://jsbin.com/fehoq/177/edit]1
JS
//example script that follows actual script
var _this = this;
//initialize my array
this. lowest = [];
// I want to compare values in lowest to values in this array
this.scores = ko.observableArray();
// method that does comparison
this.myMethod = function(){
// initialize my helper, k
var k;
...
// loop through one array
ko.utils.arrayForEach(_this.scores(), function (score) {
// make sure my value is a number...
if (!isNaN(parseFloat(score()))) {
// this is important, I need to current index for comparison
k = _this.scores.indexOf(score);
console.log(k);
// this is where things break - it prints a function, not a value!
console.log(_this.lowest[k]);
// useless check, the value is a function, so they're always different
if (score()!=_this.lowest[k]){
// do stuff
}
}
}
}
Update
Putting the method I'm using, maybe someone will notice something I missed given that my syntax is correct(?).
this.mean = (function(scores,i) {
var m = 0;
var count = 0;
var k;
ko.utils.arrayForEach(_this.scores(), function(score) {
console.log([typeof score(), score()]);
if (!isNaN(parseFloat(score()))) {
console.log(i);
console.log(_this.lowest[i]);
if (score() != _this.lowest[i]) {
m += parseFloat(score());
count += 1;
}
}
});
if (count) {
m = m / count;
return m.toFixed(2);
} else {
return 'N/A';
}
});
}
Update 2
Just in case someone else wanders over here since my problem isn't solve still. The following code is how I set the value of lowest:
this.dropLowestScores = function() {
ko.utils.arrayForEach(_this.students(), function(student){
var comparator = function(a,b){
if(a()<b()){
return 1;
} else if(a() > b()){
return -1;
} else {
return 0;
}
};
var tmp = student.scores().slice(0);
tmp.sort(comparator);
student.lowest = ko.observableArray(tmp.splice((tmp.length-2),tmp.length-1));
});
};
Outstanding Questions, 5/9/2014
Jeremy's script runs but without the desired effects. For example, console.log(_this.lowest[k]) prints undefined, just as mine does. Further, the matched scores aren't skipped, which they should be.
Jeremy's script specifies lowest as a ko.observable. My script also now has lowest as a ko.observable, but why shouldn't a plain JS array work for this? I only need lowest to update when the button it's bound to is clicked, and those bindings are already taken care of.
That is how observables work in Knockout.
When you create one, you are creating a function.
var myObservable1 = ko.observable(); // Create it.
var myObservable2 = ko.observable("Hola!"); // Create it with a value.
console.log(typeof myObservable2); // It is indeed a function
console.log(typeof myObservable2()); // That returns a string
console.log(myObservable2()); // And get the value.
EDIT BASED ON QUESTION IN COMMENTS
var koTest = ko.observableArray();
koTest.push("Line0");
koTest.push("Line1");
koTest.push("Line2");
koTest.push("Line3");
koTest.push("Line4");
var jsTest = [];
jsTest.push("Line0");
jsTest.push("Line1");
jsTest.push("Line2");
jsTest.push("Line3");
jsTest.push("Line4");
alert(koTest()[2]);
alert(jsTest[2]);
alert(koTest()[2] === jsTest[2]);
Test Code
I went ahead and make a runnable test of your code and everything was working just fine for me. I had to make some assumptions about the contents of _this -- in particular the declaration of lowest, which I made an observableArray based on how you were accessing it.
Anyways, this code runs:
var _this = {
scores: ko.observableArray(),
lowest: ko.observableArray()
};
var mean = (function(scores) {
var m = 0;
var count = 0;
var k;
ko.utils.arrayForEach(_this.scores(), function(score) {
console.log([typeof score(), score()]);
if (!isNaN(parseFloat(score()))) {
k = _this.scores.indexOf(score);
console.log(k);
console.log(_this.lowest[k]);
if (score() != _this.lowest[k]) {
m += parseFloat(score());
count += 1;
}
}
});
if (count) {
m = m / count;
return m.toFixed(2);
} else {
return 'N/A';
}
});
for (var i = 0; i < 10; i++) {
_this.scores.push(ko.observable(i));
}
var m = mean();
alert(m);