如何从另一个字符串中“减去”一个字符串？

Question

Suppose I have the following two strings:

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

I want to subtract the mask from the value . In other words I want something like this:

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

What is the best way to implement subtract() ? I have written this, but that 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;
}

Does JavaScript have something built-in to accomplish this? Note that, the masking characters are not limited to - (dash), but can be other characters as well, like + . But in a given case, the masking character can only be either - or + , which can therefore be sent to the subtract() function, which makes handling different masking character trivial. Also, the masking characters will be in arbitrary positions.

Any language-agnostic answers are also welcome.

Answer 1

You could split the value string and filter the characters which are unequal to the character at the same position of the mask string.

Then join the array for a new string.

 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 - -")); 

Answer 2

Just iterate through value and check if the corresponding value in mask is not -

  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); 

Answer 3

Mask can be any characters if you iterate through each character of value and compare to same position in mask:

Example using Array#reduce() on 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 )