supplant

supplant.js

function supplant(text, params) {
    return text.replace(/\${([^{}]*)}/g, (a, b) => {
        const r = params[b]
        return typeof r === 'string' || typeof r === 'number' ? r : a
    })
}

console.log(supplant("I'm ${age} years old!", { age: 29 }));
console.log(supplant("The ${a} says ${n}, ${n}, ${n}!", { a: 'cow', n: 'moo' }));