哪种方法更快？
数组连接：
var str_to_split = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
var myarray = str_to_split.split(",");
var output=myarray.join("");
字符串连接：
var str_to_split = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
var myarray = str_to_split.split(",");
var output = "";
for (var i = 0, len = myarray.length; i<len; i++){
output += myarray[i];
}
ECMAScript 中的字符串连接速度更快。这是我创建的一个基准测试：
从 2011 年到现代......
请参阅以下join使用字符串连接的重写，以及它比标准实现慢多少。
// Number of times the standard `join` is faster, by Node.js versions:
// 0.10.44: ~2.0
// 0.11.16: ~4.6
// 0.12.13: ~4.7
// 4.4.4: ~4.66
// 5.11.0: ~4.75
// 6.1.0: Negative ~1.2 (something is wrong with 6.x at the moment)
function join(sep) {
var res = '';
if (this.length) {
res += this[0];
for (var i = 1; i < this.length; i++) {
res += sep + this[i];
}
}
return res;
}
道德是 - 不要手动连接字符串，始终使用标准join.
我可以肯定地说使用 Array.join() 更快。我已经处理了几段 JavaScript 代码，并通过删除字符串操作以支持数组来显着提高性能。
当字符串数组已经存在时，“加入”会更快。真正的比较是比较：
对于少量的迭代和字符串，使用 push-and-join 还是 concatenate 都没有关系。但是，对于大量字符串，数组推送和连接在 chrome 和 firefox 中似乎都更快。
以下是 10 到 1000 万个字符串的代码和测试结果：
铬合金：
strings 10
join-only: 0.01171875 ms
push-join: 0.137939453125 ms
concatenate: 0.01513671875 ms
strings 100
join-only: 0.01416015625 ms
push-join: 0.13427734375 ms
concatenate: 0.0830078125 ms
strings 1000
join-only: 0.048095703125 ms
push-join: 0.47216796875 ms
concatenate: 0.5517578125 ms
strings 10000
join-only: 0.465087890625 ms
push-join: 5.47314453125 ms
concatenate: 4.9619140625 ms
strings 100000
join-only: 7.6240234375 ms
push-join: 57.37109375 ms
concatenate: 67.028076171875 ms
strings 1000000
join-only: 67.666259765625 ms
push-join: 319.3837890625 ms
concatenate: 609.8369140625 ms
strings 10000000
join-only: 824.260009765625 ms
push-join: 3207.129150390625 ms
concatenate: 5959.56689453125 ms
火狐：
strings 10
join-only: 0ms
push-join: 1ms
concatenate: 0ms
strings 100
join-only: 0ms
push-join: 0ms
concatenate: 0ms
strings 1000
join-only: 0ms
push-join: 1ms
concatenate: 0ms
strings 10000
join-only: 1ms
push-join: 2ms
concatenate: 0ms
strings 100000
join-only: 5ms
push-join: 11ms
concatenate: 8ms
strings 1000000
join-only: 39ms
push-join: 88ms
concatenate: 98ms
strings 10000000
join-only: 612ms
push-join: 1095ms
concatenate: 3249ms
测试代码：
for (var n = 10; n <= 10000000; n*=10) {
var iterations = n;
console.log("strings", iterations);
console.time("push-join");
arr = [];
for (var i = 0; i< iterations; i++) {
arr.push("a b c d e f g h i j k l m");
}
console.time("join-only");
content = arr.join(",");
console.timeEnd("join-only");
console.timeEnd("push-join");
content = "";
console.time("concatenate");
for (var i = 0; i< iterations; i++) {
content += "a b c d e f g h i j k l m";
}
console.timeEnd("concatenate");
}
这取决于：
Array Join 慢 30%
String Concat 慢 90%