Pair a specific portion of text with another string

Question

Pair a specific portion of text with another string

I'm having trouble finding a substring within a string. The substring and the string are as follows:

var str="My name is foo.I have bag(s)"
 var substr="I have bag(s)"

When I use str.match(substr), it returns null, probably because the match() function expects a regular expression input and gets confused with the '('. I tried using '\' before the round brackets, but it didn't work. The indexOf() function does work, but unfortunately, I am not allowed to use it. I also attempted using test() and exec(), but without any success.

javascript

Answer 1

Answer №1

For modern engines, you can easily utilize the String.prototype.includes method:

str.includes( substr )

If you need a solution that is compatible with older browsers and want to steer clear of using String.prototype.indexOf, you can create your own `includes` function by manually iterating through the string:

String.prototype.includes = function ( substr, start ) {
    var i = typeof start === 'number' ? start : 0;
    // Exit early if there are not enough characters left in substr for j to reach its length
    for ( var j = 0; i + substr.length < this.length + j + 1; ++i ) {
        j = substr[j] === this[i] ? j + 1 : 0;
        if ( j === substr.length )
            return true;
    }
    return false;
};

If you absolutely must use a regex test, you can follow the guidance from this particular answer to properly escape the substring for regex usage. This involves adding a backslash before certain characters like parentheses:

new RegExp( substr.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&') ).test( str )

Answer 2

For modern engines, you can easily utilize the String.prototype.includes method:

str.includes( substr )

If you need a solution that is compatible with older browsers and want to steer clear of using String.prototype.indexOf, you can create your own `includes` function by manually iterating through the string:

String.prototype.includes = function ( substr, start ) {
    var i = typeof start === 'number' ? start : 0;
    // Exit early if there are not enough characters left in substr for j to reach its length
    for ( var j = 0; i + substr.length < this.length + j + 1; ++i ) {
        j = substr[j] === this[i] ? j + 1 : 0;
        if ( j === substr.length )
            return true;
    }
    return false;
};

If you absolutely must use a regex test, you can follow the guidance from this particular answer to properly escape the substring for regex usage. This involves adding a backslash before certain characters like parentheses:

new RegExp( substr.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&') ).test( str )

Pair a specific portion of text with another string

Answer №1

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