CODEWITHSUNDEEP
javascriptjquery
ptamzz
ptamzz

Reputation: 9365

what happens to a javascript variable assign with a non existent variable

I'm assigning a javascript variable with a value as

var newline = $("#newline").val();

The $("#newline").val() may or may not exist (in some cases, the #newline may not exist in the DOM, or even if it exists, it may not have any value).

I want to check whether the var newline is set or not. How do I do that?

Upvotes: 2

Views: 435

Answers (2)

Shaz
Shaz

Reputation: 15867

jQuery:

(function() {
    if (this && this[0] && this[0].value) {
        // Has a value
    } else {
        // Has no value    
    }    
}).call($("#newline"));

this[0] is the HTML Element itself, rather than a jQuery Object.

Pure JavaScript:

(function() {
    if (this && this.value) {
        // Has a value
    } else {
        // Has no value    
    }    
}).call(document.getElementById("newline"));

Upvotes: 0

Quentin
Quentin

Reputation: 943591

This comes down to "What does the jQuery val method return if there are no elements matching the selector in the DOM?"

The answer to that is undefined so:

if ( typeof newline === "undefined" ) {

}

Upvotes: 5

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