2

I want some jquery variables to be created dynamically. In my code I am having a loop, and with the loop values I want to create some variables. Here is my sample code. 

array=["student","parent","employee"]

$.each(user_types, function( index, value ){
  var value+"_type" // this is the type of variable i want to build.
})

I have found about eval function. That code goes like this.

var type = "type"
eval("var pre_"+type+"= 'The value of dynamic variable, val';");

alert(pre_type) // this gives 'The value of dynamic variable, val' in alert box.

Is there any alternate ways as I have read the eval function is not prefered while coding .js files.

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2
  • 1
    duplicate stackoverflow.com/questions/5187530/… Commented Nov 14, 2013 at 11:50
  • 1
    var pres = {}; var type = "foo"; pres[type] = "something"; - "dynamic keys" Commented Nov 14, 2013 at 11:51

3 Answers 3

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13

Any time you find yourself using a variable in the name of a variable, you probably want to use an object literal. Create the object with curly braces {}, and then set the object property key using square bracket notation:

var user_types = ["student","parent","employee"];
var types = {};

$.each(user_types, function( index, value ){
  types[value] = 'The value of dynamic variable, val';
});

JSFiddle

Note: You haven't tagged it, but I assume because you've used each() that you are using jQuery, please correct me if I'm wrong.

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2 Comments

Thanks, I think this would be better and elegant solution than using the eval as this will not pollute my global scope. And I am using jquery over here. Let me try and will post you back.
this is most helpful for me
6

First of all i must say that i can't think of any reason why you want to do this.

If you really need to have those variables, in global scope, you can do the following:

var array=["student","parent","employee"]

array.forEach(function(value){
  window[value+"_type"] = 'My value ' + value;
});

console.log(student_type);
console.log(parent_type);
console.log(employee_type);

If you don't want the variables in global scope, i'm afraid i don't know an elegant solution.

I used array.forEach instead of your jQuery loop because the problem is not related to jQuery at all and because i don't think you said enough of your logic to make a coherent example.

EDIT: I should make it clear that while the 'variables' created behave mostly like other variables in global scope, they are NOT variables. Here is how they differ:

// Difference 1: hoisting
console.log(x); // undefined
console.log(y); // ReferenceError: y is not defined
var x = 5;
window[y] = 5;
console.log(x); // 5
console.log(y); // 5
// Difference 2: [[Configurable]] 
delete x;
delete y;
console.log(x); // 5
console.log(y); // ReferenceError: y is not defined
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2 Comments

Thanks for the enlightment. I have made up my mind for using eval funtion. I wanted to created some custom names that will be dynamically generated and can store some values. I can achieve by the way that oGeez has mentioned below. I tried it with windows, works fine. But I found the other way was better to deal with my case.
@DeepakA I'm glad. As i said in the first line, i don't think there is ever a reason to do what i wrote in this post :). The knowledge doesn't hurt though.
0

If you want to add an intermediate variable inside the string, you can do it as follows:

var itemSelect: number = 1;
$(`#tab${this.itemSelect}-tab`).tab('show');
/* Result -> $(`#tab1-tab`).tab('show');  */

/* HTML */
<a id="tb1-tab"> </a>
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