gaurav gaurav - 5 years ago 158
Javascript Question

How to check 'undefined' value in jquery


Possible Duplicate:

Detecting an undefined object property in JavaScript

javascript undefined compare




How we can put a check for undefined like:

function A(val){
if(val == undefined)
//do this
else
//do this
}

Answer Source

JQuery library was developed specifically to simplify and to unify certain JavaScript functionality.

However if you need to check a variable against undefined value, there is no need to invent any special method, since JavaScript has a typeof operator, which is simple, fast and cross-platform:

if (typeof value === "undefined") {
    // ...
}

It returns a string indicating the type of the variable or other unevaluated operand. The main advantage of this method, compared to if (value === undefined) { ... }, is that typeof will never raise an exception in case if variable value does not exist.

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