Question 234291 in Javascript Question posted in
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Regex remove repeated +-*/ characters from a string by javascript

I need reg expression.
I do calculator, and this string appear at my view side of app.
How to get this “111+22-33*4” from this “111+++22-33*****4”

Or another example
How to get “22243+11” from “22243++++11”

“565656565656565656565”

Tags:

2

Answers


  1. 0

    Here’s how to do this with a simple loop.

    function strip(s) {
    var out = "";
    var last = 'X';
    for( let i = 0; i < s.length; i++ )
    {
        const c = s[i];
        if( "+-*/".indexOf(c) < 0 || c != last )
        {
            out = out + c;
        }
        last = c;
    }
    return out;
}

console.log( strip("2222++++444"));
console.log( strip("111+++222***333///444+-5"));
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  2. 0 
    console.log('+-111+++22-33*****4//////3'.replace(/([-/*+])1+/g, '$1'));

    Analysis:

    ([-/*+]) – capture your target character to replace into a capture group
    1+ – match any number of repeating captured character
    /g – global replace
    $1 – replace with 1 captured character

    An Array::reduce() one-liner:

    const str = '+-111+++22-33*****4//////3';

const res = str.split('').reduce((r,c,i,arr) => i && arr[i-1] === c && '*/+-'.includes(c) ? r : r + c, '');

console.log(res);

    And a benchmark:

    enter image description here

    <script benchmark data-count="1000000">

const str = '+-111+++22-33*****4//////3';

// @benchmark Tim
function strip(s) {
    var out = "";
    var last = 'X';
    for( let i = 0; i < s.length; i++ )
    {
        const c = s[i];
        if( "+-*/".indexOf(c) < 0 || c != last )
        {
            out = out + c;
        }
        last = c;
    }
    return out;
}
//@run
strip(str)

// @benchmark regexp
str.replace(/([-/*+])1+/g, '$1');

// @benchmark Array::reduce()
str.split('').reduce((r,c,i,arr) => i && arr[i-1] === c && '*/+-'.includes(c) ? r : r + c, '');

</script>
<script src="https://cdn.jsdelivr.net/gh/silentmantra/benchmark/loader.js"></script>
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