1.for循环

1
2
3
4
var arr = [1,2,3,4];
for(var i= 0; i< arr.length; i++) {
console.log(arr[i]);
}

等同于:

1
2
3
for(var item of arr) {
console.log(item);
}

2.十进制数

1
2
3
setTimeout(function(){
console.log('done');
},1000);

等同于:

1
2
3
setTimeout(function(){
console.log('done');
},1e3);
  1. Array.find
1
2
3
4
5
6
7
8
9
10
11
12
const pets = [
{ type: 'Dog', name: 'Max'},
{ type: 'Cat', name: 'Karl'},
{ type: 'Dog', name: 'Tommy'},
]
function findDog(name) {
for(let i = 0; ii) {
if(pets[i].type === 'Dog' && pets[i].name === name) {
return pets[i];
}
}
}

等同于:

1
2
pet = pets.find(pet => pet.type ==='Dog' && pet.name === 'Tommy');
console.log(pet); // { type: 'Dog', name: 'Tommy' }

4.双位操作符

1
Math.floor(4.9) === 4  //true

可以使用双位运算符代替上面的写法:

1
~~4.9 === 4  //true