Javascript RegEx Find Variable String Without Substring?

Question

var str = "Visit tEsT!"; 
var ara = "test";
let n = str.search(/\b + ara + \b/i); // Sadly code doesn't run
document.getElementById("demo").innerHTML = n;

I want find ara variable in str variable with regex search().

İ want find "ara" variable in "str" variable with regex search(). — Soru İşareti, Jan 29 '20 at 15:43

ButchMonkey · Accepted Answer · 2020-01-29T15:51:04.433

3

You need to define a new regex from a string in order to use variables.You can do this with new RegExp(). You will also need the i option for case insensitive mode.

var str = "Visit tEsT!"; 
var ara = "test";
var regex = new RegExp(`\\b${ara}\\b`, 'i'); // Evaluates to "/\btest\b/i"
let n = str.search(regex);
document.getElementById("demo").innerHTML = n;

edited Jan 29 '20 at 15:51

answered Jan 29 '20 at 15:43

ButchMonkey

1,873
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Thank you for fastly help :) – Soru İşareti Jan 29 '20 at 15:47
ara.replace(/[&\/\\#,+()$~%.'":*?<>{}]/g, '') @FZs – Soru İşareti Jan 29 '20 at 15:58

Ritesh Khandekar · Answer 2 · 2020-01-29T16:29:38.217

2

You have to put variables like this in Regex:

var str = "Visit tEsT!"; 
var ara = "test";
let n = str.search(new RegExp(`\\b${ara}`,"i")); 
console.log(n);

More secure way is to remove special chars:

str.replace(/[^A-Za-z0-9\s\n]/g,"")

var str = "Visit tEsT!"; 
var searchstr = "test &#";
let n = str.search(new RegExp(`\\b${searchstr.replace(/[^A-Za-z\\s\\n]/g,"")}`,"i")); 
console.log(n);

edited Jan 29 '20 at 16:29

answered Jan 29 '20 at 15:43

Ritesh Khandekar

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Thank you for fastly help :) – Soru İşareti Jan 29 '20 at 16:03

SparkFountain · Answer 3 · 2020-01-29T15:48:04.470

1

In your regular expression, you cannot use the + operator as a string concatenator. Instead, you could use for example template strings and create the regular expression with new RegExp:

var str = "Visit tEsT!"; 
var ara = "test";
var regex = new RegExp(`\\b${ara}\\b`, 'gi');  // use 'gi' flags to search globally and ignore case
let n = str.search(regex);
console.log(n);

edited Jan 29 '20 at 15:48

answered Jan 29 '20 at 15:45

SparkFountain

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You can use `+` for concatenation. You also need to escape `\b` – ButchMonkey Jan 29 '20 at 15:46
Thank you for fastly help :) – Soru İşareti Jan 29 '20 at 15:47
1

@ButchMonkey Thanks for your advice. I thought I had to double escape but the PlayCode.io syntax highlighting confused me... – SparkFountain Jan 29 '20 at 15:48
NP. I should clarify that you can use `+` for concatenation in `new RegExp` as it creates a regex from string. But you are correct that you cannot use `+` in `/.*/g` syntax as it will be evaluated – ButchMonkey Jan 29 '20 at 15:55

score 1 · Answer 4 · answered Jan 29 '20 at 15:56

1

If you want the matched string, use match() instead. The return value n will be an array and its first value (n[0]) will be the matched string.

var str = "Visit tEsT!"; 
var ara = "test";
var regexp = new RegExp("\\b"+ara+"\\b", 'gi')
n = str.match(regexp);
document.getElementById("demo").innerHTML = n[0];

answered Jan 29 '20 at 15:56

PHP Guru

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11
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Thank you for your help too i maked search engine for my blog but if i use indexOf() visitor search value "a" then it show all articles ... İ just want to filter with regex to make results better... – Soru İşareti Jan 29 '20 at 16:05
Why do you want to show the index of the matched expression? That's what String.prototype.search() does. – PHP Guru Jan 29 '20 at 16:13
`let str = 'B ad ga'; let result = str.search('a'); document.write(result);` but when i run this code, answer is: "2" so search() like indexOf() – Soru İşareti Jan 29 '20 at 16:54
Yes. It's exactly like indexOf except it expects a regular expression. – PHP Guru Feb 01 '20 at 21:46

score 1 · Answer 5 · answered Jan 29 '20 at 16:29

Using search and match multiple ways.

var str = "Visit tEsT!"; 
var ara = "test";
let n = str.search(new RegExp('\\b' + ara + '\\b', 'i'))

let n2 = str.match(new RegExp('\\b' + ara + '\\b', 'i')).index;

//document.getElementById("demo").innerHTML = n;

console.log(n, n2)

Javascript RegEx Find Variable String Without Substring?

5 Answers5