what is the best way to check if a string exists in another?

Question

Possible Duplicate:
JavaScript: string contains

I'm looking for an algorithm to check if a string exists in another.

For example:

'Hello, my name is jonh LOL.'.contains('Hello, my name is jonh'); //true
'LOL. Hello, my name is jonh'.contains('Hello, my name is jonh'); //true

Thanks in advance.

Here a benchmark for the most common ways to check if a string is in a string: http://jsben.ch/#/o6KmH — EscapeNetscape, Oct 31 '16 at 17:06

Digital Plane · Accepted Answer · 2011-09-01T16:42:59.927

28

Use indexOf:

'Hello, my name is jonh LOL.'.indexOf('Hello, my name is jonh') > -1; //true
'LOL. Hello, my name is jonh'.indexOf('Hello, my name is jonh') > -1; //true

You can also extend String.prototype to have a contains function:

String.prototype.contains = function(substr) {
  return this.indexOf(substr) > -1;
}
'Hello, my name is jonh LOL.'.contains('Hello, my name is jonh'); //true
'LOL. Hello, my name is jonh'.contains('Hello, my name is jonh'); //true

edited Sep 01 '11 at 16:42

answered Sep 01 '11 at 16:26

Digital Plane

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further to this answer, you could create `function contains(haystack, needle) { return haystack.indexOf(needle) > -1; }` Or even create one on the String prototype – Jonathan Fingland Sep 01 '11 at 16:30
@Jonathan I added a `String.prototype` function. – Digital Plane Sep 01 '11 at 16:31

score 1 · Answer 2 · answered Sep 01 '11 at 16:32

As Digital pointed out the indexOf method is the way to check. If you want a more declarative name like contains then you can add it to the String prototype.

String.prototype.contains = function(toCheck) {
  return this.indexOf(toCheck) >= 0;
}

After that your original code sample will work as written

Joe · Answer 3 · 2011-09-01T16:45:25.480

1

How about going to obscurity:

!!~'Hello, my name is jonh LOL.'.indexOf('Hello, my name is jonh'); //true
if(~'LOL. Hello, my name is jonh'.indexOf('Hello, my name is jonh'))
    alert(true);

Using Bitwise NOT and to boolean NOTs to convert it to a boolean than convert it back.

edited Sep 01 '11 at 16:45

answered Sep 01 '11 at 16:35

Joe

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although this works, `val > -1` is fewer operations – zzzzBov Sep 01 '11 at 16:40
@zzzzBov, technically the !! Is unnecesary. So just the tilde would work. – Joe Sep 01 '11 at 16:44
...depending on how strictly you need a boolean value. I agree, `~` will output the correct falsey state. – zzzzBov Sep 01 '11 at 16:45

clarkb86 · Answer 4 · 2011-09-01T16:36:12.237

0

I would suppose that using pre-compiled Perl-based regular expression would be pretty efficient.

RegEx rx = new Regex('Hello, my name is jonh', RegexOptions.Compiled);
rx.IsMatch('Hello, my name is jonh LOL.'); // true

edited Sep 01 '11 at 16:36

answered Sep 01 '11 at 16:30

clarkb86

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I'm using JavaScript, but thanks :P – The Mask Sep 01 '11 at 16:41
Even better: `var regex = /Hello, my name is jonh/; regex.test("Hello, my name is jonh LOL."); // true` – clarkb86 Sep 01 '11 at 16:48

score 0 · Answer 5 · answered Sep 01 '11 at 16:30

0

another option could be to match a regular expression by using match(): http://www.w3schools.com/jsref/jsref_match.asp.

> var foo = "foo";
> console.log(foo.match(/bar/));
null
> console.log(foo.match(/foo/));
[ 'foo', index: 0, input: 'foo' ]

answered Sep 01 '11 at 16:30

marcelog

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what is the best way to check if a string exists in another?

5 Answers5