JavaScript - Searching for a char in string using indexOf()

Question

When verifying that character is NOT in string, is it both the same when using if(string.indexOf("x") < 0) { ... } or if(string.indexOf("x") == -1) { ... }?

Could there be some circumstances when string.indexOf("x") would be -2 or lower?

Thank you for sharing your experiences.

No, It will always be -1 if sub string not found in the string. There is no chance to return values below that. — Rajaprabhu Aravindasamy
– Rajaprabhu Aravindasamy, Commented Apr 11, 2016 at 13:08
The indexOf() method returns the position of the first occurrence of a specified value in a string. This method returns -1 if the value to search for never occurs. w3schools.com/jsref/jsref_indexof.asp — vaso123
– vaso123, Commented Apr 11, 2016 at 13:09

Roy · Accepted Answer · 2016-04-11 13:09:39Z

2

Could there be some circumstances when string.indexOf("x") would be -2 or lower?

No. It cannot. Index is negative (-1) only when there is no match.

When verifying that character is NOT in string, is it both the same when using if(string.indexOf("x") < 0) { ... } or if(string.indexOf("x") == -1) { ... }

Of course they are the same because -1<0.

answered Apr 11, 2016 at 13:09

Roy

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Dmitri Pavlutin · Accepted Answer · 2016-04-11 13:15:15Z

2

According to indexOf() specification, it can return a value: -1 (if substring not found) and from 0 up to string.length - 1 (indicating the match position).

A better approach is to use the ECMAScript 6 method includes():

var string = 'x-files';

string.includes('x'); // prints true

edited Apr 11, 2016 at 13:15

answered Apr 11, 2016 at 13:09

Dmitri Pavlutin

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Comments

brso05 · Accepted Answer · 2016-04-11 13:09:17Z

1

They are the same:

"The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present."

MDN

answered Apr 11, 2016 at 13:09

brso05

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