Is there a way to refer to a Javascript variable with a string that contains its name?
example:
var myText = 'hello world!';
var someString = 'myText';
//how to output myText value using someString?
-
See: stackoverflow.com/questions/724857/…Crescent Fresh– Crescent Fresh2009-11-03 00:53:56 +00:00Commented Nov 3, 2009 at 0:53
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7 Answers
You can use an eval to do it, though I try to avoid that sort of thing at all costs.
alert(eval(someString));
A better way, if you find yourself needing to do this, is to use a hash table.
var stuff = { myText: 'hello world!' };
var someString = 'myText';
alert( stuff[someString] );
3 Comments
CJT3
if I'd rather use the window['varname']; approach, how would I do it using with an object?
var obj = {'eleID':'varname'}; for (var key in obj) { window[obj[key]]; } This doesn't seem to work :(
Tron
I keep seeing people saying to avoid using eval for this and similar questions - but why?
BobtheMagicMoose
@Tron mainly because you don't control someString, but you are letting it to run as though you did. It could be malicious, have coding errors, or other nightmare-inducing issues. Imagine someString were "while(1){}" or a script that sent data to a malicious server.
If that variable is on the global scope, you can use the bracket notation on the global object:
var myText = 'hello world!';
var someString = 'myText';
alert(window[someString]);
answered Nov 2, 2009 at 23:03
Christian C. Salvadó
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2 Comments
Lemex
Amazing answer saves the use of eval +1 wish i could + 10
jerclarke
So goOD! Thank you! This is what I was looking for!
eval() worked for my main case, but I couldn't check if the variable I was using eval() to exercise was defined or not. typeof window[event.data.lingua_target_content_var] !== 'undefined' works when eval() threw an error!Assuming this is at the top level, window[someString] === "hello world!".
Comments
In JavaScript, there is no standard for creating a 'Master Object', or any built-in method to access variables on the initial scope with a string reference that I am aware of.
However, if you are using JavaScript for web development on a browser, the window Object will give you complete access to your current scope. For example:
myVar = "This is my var";
if(myVar == window.myVar){
/*
This statement would return true
Because both variables reference
the same string;
*/
}
This method will allow you to reference any scope-variable WITHOUT making it a string, but you can also use a string as needed with the bracket ([]) Selectors.
window['myVar']
It is worth mentioning that keeping data as a variable directly on the current scope leaves it open to be re-defined by other scripts running. Your variable can be overwritten by function argument names, for loop variables, and simply by assigning a new value to that variable.
To overcome this, I suggest using an Object to store all relevant data to your application (Static And/Or OOP). Like this:
$myApp = {
var1 : 'This is Var1',
apply : function(){
alert('Started!');
}
}
//Referencing relative variables
alert($myApp.var1);
Comments
You can do this with eval:
var myText = 'hello world!';
var someString = 'myText';
eval('var theTextInMyText = ' + someString + ';');
alert(theTextInMyText);
The desire to do this at all usually is a "code smell". Perhaps there is a more elegant way...
Comments
eval will do that:
var myText = 'hello world!!';
var someString = eval('myText');
document.getElementById('hello').innerHTML = someString;
Comments
eval("alert(" + someString + ");");
would work.
