js合并字符串的3种方法和效率

/* abc abc abc*/

function concat(s,n)
{
    let a = new Array(n);
    a.fill(s);
    let str = a.join('');
    a = null;
    return str;
}

function concat1(s, n){
    let count = n;
    let str = '';
    while(count > 0)
    {
        str += s;
        count --;
    }
    return str;
}
function tco(f) {
    var value;
    var active = false;
    var accumulated = [];
    return function accumulator() {
        accumulated.push(arguments);
        if(!active) {
            active = true;
            while(accumulated.length) {
                value = f.apply(this, accumulated.shift());
            }
            active = false;
            return value;
        }
    };
}
const concat2 = tco(function ( s,n, ret = '')
{
    if(n == 1) return s+ret;
    return concat2(s, n-1, ret+s);
})
let n = 10000*100;
let startTime =  new Date();
let str = concat('abc',n);
let endTime = new Date();

let str1 = concat1('abc',n);
let endTime1 = new Date();
let str2 = concat2('abc',n);
//console.log('the result is \"'  + str2 + '\"');
let endTime2 = new Date();
//console.log('the result is \"'  + str + '\"');
console.log('time:' + (endTime.getTime() - startTime.getTime()));
console.log('time1:' + (endTime1.getTime() - endTime.getTime()));
console.log('time2:' + (endTime2.getTime() - endTime1.getTime()));

1. 10000*100

time:135
time1:364
time2:684

2：10000*1000

time:1357

time1:7395

time2:6883

 

time:1357time1:7395time2:6883