regex match begining using variable

Question

So i want this correct match() syntax with variable var a = 'breaksmooth'; and var b = 'bre'; , what i knew if i'm not using any variable or at least search in variable : if(a.match(/^bre/)) return true; i just want to achieve this if(a.match(/^b/); where b is var b which is give me error .i dont want to change var b with b = /^bre/. any solution ?

Possible duplicate of Use dynamic (variable) string as regex pattern in JavaScript — helloitsjoe
– helloitsjoe, Commented Jul 20, 2019 at 13:51

Rishab · Accepted Answer · 2019-07-20 13:52:30Z

1

Use this method:

var a = 'breaksmooth';
var b = 'bre';
var re = new RegExp(b, 'g');
a.match(re)

answered Jul 20, 2019 at 13:52

Rishab

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2 Comments

Rishab Over a year ago

g flag is for global match.

melpomene Over a year ago

And what do you mean by "global match"?

melpomene · Accepted Answer · 2019-07-20 14:16:46Z

0

If you just want to check whether a starts with b, you don't need a regex at all:

var a = 'breaksmooth';
var b = 'bre';
if (a.startsWith(b)) {
    console.log('yes');
}

See the startsWith method.

On the other hand, if you want to create a regex from a string, you can use the RegExp constructor:

var b = 'bre';
var regex = new RegExp('^' + b);  // same as /^bre/

You don't even need a separate variable:

if (a.match(new RegExp('^' + b))) {

answered Jul 20, 2019 at 14:16

melpomene

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