CODEWITHSUNDEEP
javascriptjquery
user1464139
user1464139

Reputation:

How can I check if the value of a parameter passed to a javascript function is null?

I have the following javascript code:

    function changeButtonState(targetSelector, action, iconClass) {
        var $target = $(targetSelector);
        var $targetSpan = $(targetSelector + ' span');
        $targetSpan.removeClass('sprite-blank').addClass(iconClass);

How can I make it so that the $targetSpan.removeClass(..).addClass only work if the iconClass has a value when the function is called. I guess what I am confused about is do I check if it is defined or do I check if it has a length of 0 or more?

Upvotes: 4

Views: 3050

Answers (2)

Sang Suantak
Sang Suantak

Reputation: 5265

It would be best if you check for undefined as well. 

function changeButtonState(targetSelector, action, iconClass) {    
    var $target = $(targetSelector);
    if (typeof iconClass !== "undefined" && iconClass) {
        var $targetSpan = $(targetSelector + ' span');
        $targetSpan.removeClass('sprite-blank').addClass(iconClass);
    }
}​

Update Even though this is a very old answer, it is still relevant. Therefore, i would like to update my answer with an improved one based on @jeremy's comment.

function changeButtonState(targetSelector, action, iconClass) {    
    var $target = $(targetSelector);
    //this will not throw exception since iconClass is implicitly declared through the input parameter 
    if (iconClass) {
        var $targetSpan = $(targetSelector + ' span');
        $targetSpan.removeClass('sprite-blank').addClass(iconClass);
    }
}​

Upvotes: 3

jeremy
jeremy

Reputation: 10057

This would allow the user (most likely you) to specify whether or not you want it to be active by either giving it a falsey value or a truthy value. You may also want to check if it's undefined by using the typeof operator.

if(iconClass) {
    $targetSpan.removeClass('sprite-blank').addClass(iconClass);
}

Upvotes: 1

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