String To String Literal Template

string_literals.js

/** Generate a string literal template with arbitrarily many substitutions.
 * Usage: (IMPORTANT, MUST OMIT BRACKETS IN THE INSTANTIATION CALL):
 * let template = stringLiteralTemplate`Hello, ${0}. This is a ${1}`;
 * let final_string = template.with('world', 'test');
 * >> "Hello, world. This is a test"
 * Also:
 * let template = stringLiteralTemplate`${0}, ${0}, ${1}. ${2}. ${2} 1, 2, 3.`;
 * let final_string = template.with('Hello', 'World', 'Testing');
 * >> "Hello, Hello, World. Testing. Testing 1, 2, 3"
 */
export const stringLiteralTemplate = (literals, ...substitutions) => ({

    with() {

        let out = [], i, k;

        for (i = 0, k = 0; i < literals.length; i++) {
            out[k++] = literals[i];
            out[k++] = arguments[substitutions[i]];
        }

        out[k] = literals[i];
        
        return out.join('');
    }
}),

/**
 * Convert a string into a string literal template.
 * Usage:
 * let template = toStringLiteralTemplate('Hello, ${0}. This is a ${1}`);
 * let final_string = template.with('world', 'test');
 * >> "Hello, world. This is a test"
 */
export const toStringLiteralTemplate = (str) => {

    const arr = str.split(/\$\{\d+\}/g); 

    return stringLiteralTemplate(arr, ...(new Array(arr.length).fill(0).map((d,i) => i)));
},