In javascript, is an empty string always false as a boolean?

javascript string boolean
cc young picture cc young · Jan 1, 2012 · Viewed 88.6k times · Source

in javascript,

var a = '';
var b = (a) ? true : false;

var b will be set to false.

is this a defined behavior that can be relied upon?

Answer

Arenielle picture Arenielle · Jan 1, 2012

Yes. Javascript is a dialect of ECMAScript, and ECMAScript language specification clearly defines this behavior:

ToBoolean

The result is false if the argument is the empty String (its length is zero); otherwise the result is true

Quote taken from http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf

Related questions

How do I compare string and boolean in Javascript?

I got the Json "false" from server. I respond as bool but it's Json so it's in browser type is String instead of bool. So if I run (!data) whenever I want to check "false" == false then they not worked. …

Read More
How to check whether a string contains a substring in JavaScript?

Usually I would expect a String.contains() method, but there doesn't seem to be one. What is a reasonable way to check for this?

Read More
How to replace all occurrences of a string?

I have this string: "Test abc test test abc test test test abc test test abc" Doing: str = str.replace('abc', ''); seems to only remove the first occurrence of abc in the string above. How can I replace all …

Read More