JavaScript format()

function format(str, ...args){
    return str.split(/(%)/).map(part => (part == "%") ? (args.shift()) : (part)).join("");
}

// Example use: format("Hello %, you have visited % times. You are %% of the way there.", username, numVisits, percent, "%")
// "Hello Troomp, you have visited 420 times. You are 69% of the way there."