var命令存在变量提升效用,let命令没有这个问题。
'use strict';
if (true) {
console.log(x); // ReferenceError
let x = 'hello';
}
// bad
var a = 1, b = 2, c = 3;
// good
const a = 1;
const b = 2;
const c = 3;
// best
const [a, b, c] = [1, 2, 3];
字符串
// bad
const a = "foobar";
const b = 'foo' + a + 'bar';
// acceptable
const c = `foobar`;
// good
const a = 'foobar';
const b = `foo${a}bar`;
const c = 'foobar';
class
// bad
function Queue(contents = []) {
this._queue = [...contents];
}
Queue.prototype.pop = function() {
const value = this._queue[0];
this._queue.splice(0, 1);
return value;
}
// good
class Queue {
constructor(contents = []) {
this._queue = [...contents];
}
pop() {
const value = this._queue[0];
this._queue.splice(0, 1);
return value;
}
}