数组和字符串的转换

join 将数组拼接为字符串

var arr = ["html","css","javascript"]
console.log(arr.join()); // html,css,javascript
console.log(arr.join("|")); // html|css|javascript
console.log(arr.join(""));  // htmlcssjavascript

split( ) 将字符串分割成字符串数组

var str = "hello"
console.log(str.split()); // 将字符串转为数组 ["hello"]
console.log(str.split("")); // ["h","e","l","l","o"]
console.log(str.split("e"));// ["h","llo"]