语法如下:
str.concat(string2[, string3, ..., stringN])
示例:
var hello = ‘Hello, ‘;
console.log(hello.concat(‘Kevin‘, ‘ have a nice day.‘));
/* Hello, Kevin have a nice day. */
var greetList = [‘Hello‘, ‘ ‘, ‘Venkat‘, ‘!‘];
"".concat(...greetList); // "Hello Venkat!"
"".concat({}); // [object Object]
"".concat([]); /// ""
"".concat(null); // "null"
"".concat(true); // "true"
"".concat(4, 5); // "45"
"".concat({}); // [object Object]
原文：http://www.cnblogs.com/spring87/p/6684157.html