How is the '===' operator used in jQuery?

Question

taken from http://jsfiddle.net/7huEr/220/

I don't understand the line

return $.trim(this.value) === "";

I'm guessing it's returning all the input fields whose val are empty...but can someone explain how .trim and === work together?

score 1 · Accepted Answer · answered Apr 20 '14 at 00:49

1

Basically its returning the boolean true or false. it returns true if the value is completely empty, or contains white space only. it returns false otherwise.

answered Apr 20 '14 at 00:49

srg2k5

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are `==' and `===` interchangeable? – mango Apr 20 '14 at 00:49
== is loosely equal === is strictly equal – megawac Apr 20 '14 at 00:51
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=== checks the type. In this it means, an empty string. == does not make a type check. – html_programmer Apr 20 '14 at 00:51
no. === is type cast evaluator as well, while == does not check the type (float, int, str, etc) – srg2k5 Apr 20 '14 at 00:51
@KimGysen: They both check the types. It's what they do with that type information that may cause them to behave differently. – cookie monster Apr 20 '14 at 01:12

score 1 · Answer 2 · answered Apr 20 '14 at 00:51

jQuery.trim trims whitespaces from a string. So when you compare resulting string with "" for exact match (type and value) you check for empty input.

Note that unlike == which can compare "1" and 1, === verifies both value and type match. So it generally preferred to use === when type of result is known.

score 1 · Answer 3 · answered Apr 20 '14 at 00:53

The $.trim() function removes all newlines, spaces (including non-breaking spaces), and tabs from the beginning and end of the supplied string. If these whitespace characters occur in the middle of the string, they are preserved.

In your Example, It returns True if the Value is null.

Incase if the user entered many spaces without any other characters it will return True

How is the '===' operator used in jQuery?

3 Answers3