SOURCE

function once(f, obj) {
    let count = 0;
    let result;
    return function() {
        count++;
        if (count == 1) {
            if (obj == undefined) {
                obj = {};
            }
            result = f.apply(obj, arguments);
        }
        return result;
    }
}
let doPayment = once(() => {
    console.log("生死由命，富贵在天")
})
doPayment() //生死由命，富贵在天