format string to another string format javascript

Question

I have the following function:

export const getFormatValue = (raw, value) => {
 let maskIndex = 0;
 let formattedValue = '';
 raw.split('').forEach(char => {
 if (value.length > maskIndex && value[maskIndex] === ' ') {
 formattedValue += ' ';
 maskIndex += 1;
 }
 formattedValue += char;
 maskIndex += 1;
 });
 return formattedValue;
};

It fails the following test cases

Expected: "A BB CCC"
Received: "A B BC C C"
> 11 | expect(getFormatValue('ABBCCC', 'A AA AAA')).toBe('A BB CCC');

My code works for simple cases such as:

expect(getFormatValue('23', '0 0000 0000 0000')).toBe('2 3');

But soon as the "mask" pattern gets more complicated it fails.

The "mask" value is dynamic

Answer 1

You can reverse the string to be formatted, and then you can use the function Array.prototype.reduce and check the char in the pattern.

function getFormatValue(str, pattern) {
 const reversed = str.split("").reverse();
 return pattern.split("").reduce((a, c) => [...a, c === " " ? c : reversed.pop()], []).join("");
}
console.log(getFormatValue('ABBCCC', 'A AA AAA'));

Answer 2

One simple way of doing this:

export const getFormatValue = (raw, value) => {
 raw = raw.split('');
 return value.replace(/[^\s]/g, () => {
 return raw.shift() || '';
 });
}