Check if an array item is set in JS

Question

I've got an array

    var assoc_pagine = new Array();     assoc_pagine["home"]=0;     assoc_pagine["about"]=1;     assoc_pagine["work"]=2; 

I tried

    if (assoc_pagine[var] != "undefined") { 

but it doesn't seem to work

I'm using jquery, I don't know if it can help

Thanks

Answer 1

Use the in keyword to test if a attribute is defined in a object

if (assoc_var in assoc_pagine) 

OR

if ("home" in assoc_pagine) 

---

There are quite a few issues here.

Firstly, is var supposed to a variable has the value "home", "work" or "about"? Or did you mean to inspect actual property called "var"?

If var is supposed to be a variable that has a string value, please note that var is a reserved word in JavaScript and you will need to use another name, such as assoc_var.

var assoc_var = "home"; assoc_pagine[assoc_var] // equals 0 in your example 

If you meant to inspect the property called "var", then you simple need to put it inside of quotes.

assoc_pagine["var"] 

Then, undefined is not the same as "undefined". You will need typeof to get the string representation of the objects type.

This is a breakdown of all the steps.

var assoc_var = "home";  var value = assoc_pagine[assoc_var]; // 0 var typeofValue = typeof value; // "number" 

So to fix your problem

if (typeof assoc_pagine[assoc_var] != "undefined")  

---

update: As other answers have indicated, using a array is not the best sollution for this problem. Consider using a Object instead.

var assoc_pagine = new Object(); assoc_pagine["home"]=0; assoc_pagine["about"]=1; assoc_pagine["work"]=2;