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How to "subtract" one line from another?

Suppose I have the following two lines:

var value = "1-000-111";
var mask = " -   -";

I want to subtract mask

from value

. In other words, I want something like this:

var output = subtract(value, mask);
// output should be 1000111

What's the best way to implement it subtract()

? I wrote this, but it doesn't seem elegant to me.

function subtract(value, mask) {
    while (mask.indexOf('-') >= 0) {
        var idx = mask.indexOf('-');
        value = value.substr(0, idx) + value.substr(idx + 1);
        mask = mask.substr(0, idx) + mask.substr(idx + 1);
    }
    return value;
}

Is there something built-in in JavaScript to accomplish this? Note that escape characters are not limited to -

(dash), but can be other characters, for example +

. But in this case, the escape character can be either -

or +

, which can therefore be sent to a function subtract()

, making it trivial to handle another escape character. In addition, masking characters will be in arbitrary positions.

Any language agnostic answers are also appreciated.

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3 answers


You can split the string of values ​​and filter for characters that are not equal to a character at the same place in the mask string.

Then join the array to a new line.



function subtract(value, mask) {
    return value.split('').filter(function (a, i) {
        return a !== mask[i];
    }).join('');
}

console.log(subtract("1-000-111", " -   -"));
console.log(subtract("foo1-000-111", "foo -   -"));
Run code


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Just loop over the value and check if the value doesn't match mask

- 



    var value = '1-000-111';
    var mask  = ' -   -';
    
    var result = '';
    for (var i = 0; i < value.length; i += 1) {
        if (mask[i] !== '-') {
            result += value[i];
        }
    }
    
    console.log(result);
Run code


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The mask can be any character as long as you iterate over each character of the value and compare it to the same position in the mask:

Array # reduce () example for split () value

var value = "1-000-111";
var mask = " -   -";

var unmasked  = value.split('').reduce((a,c,i) => (mask[i] === c) ? a : a+c);

console.log(unmasked )
Run code


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