util.ts

// Returns a mapper function to split a string into an array of strings of the given length.
function getMapper(length: number) {
    return (a: string[], x: string, i: number) => {
        if (i % length == 0) a.push("");
        return (a[a.length - 1] += x), a;
    };
}

// Pads the given string with zeros to the left, and splits it into an array of strings of the given length.
export function padStart(data: string, length: number): string[] {
    return [
        ...Array((length - (data.length % length)) % length).fill("0"),
        ...data
    ].reduce(getMapper(length), []);
}

// Pads the given string with equals signs to the right, and splits it into an array of strings of the given length.
export function padEnd(data: string, length: number): string[] {
    return [
        ...data,
        ...Array((length - (data.length % length)) % length).fill("=")
    ].reduce(getMapper(length), []);
}

// Creates an array of numbers from 0 to length - 1, and multiplies each number by the given multiplier.
export function quickMap(
    length: number,
    multiplier: (x: number) => number,
    reverse: boolean = false
) {
    return Array(length)
        .fill(0)
        .map((_, x) => multiplier(reverse ? -x + length - 1 : x));
}

// Converts the given string to a number using the given character set.
export function stringToNumber(str: string, charset: string) {
    return str
        .split("")
        .reverse()
        .map(x => charset.indexOf(x))
        .reduce((a, x, i) => a + (x >= 0 ? x * charset.length ** i : 0), 0);
}