Handling JavaScript null string concatenation [duplicate]

Question

Why is it in JavaScript that null+'' === 'null' ?

At least this is the case on Chrome 68.

It doesn't make a sense to me. Different languages handle it differently of course, but I would assume either null or '' to be a better answer.

It just makes it hard to check if something is 'null' or if it is null + ''. Which could happen in a text field for example.

This is particularly an issue with ECMAScript 6 where you can do

value={\`${value}`}

etc.

To answer in simple language, + operator does 2 things, add or concat. if one of value is not getting converted to int, it converts both values to string using internal string function. For sample you can try String(null); This returns you "null" and hence it is equal. Hope that addresses your query — Rajesh Dixit
– Rajesh Dixit, Commented Sep 5, 2018 at 6:01

Karan Singh Dhir · Accepted Answer · 2018-09-05 05:52:25Z

0

By doing console.log(null+'') which is adding an empty string to null, you are just converting null to a string.

Look at some of the examples below:

var first = 100 + '';
var second = 10 + '' + 2;
var third = undefined + '';
var fourth = null + '';

console.log(typeof first);
console.log(typeof second);
console.log(typeof third);
console.log(typeof fourth);

answered Sep 5, 2018 at 5:52

Karan Singh Dhir

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