JS单竖杠的作用
这里介绍|的作用
console.log(0.6|0)//0
console.log(1.1|0)//1
console.log(3.65555|0)//3
console.log(5.99999|0)//5
console.log(-7.777|0)//-7
看了上面的例子，大体知道单竖杠可以进行取整运算，就是只保留正数部分，小数部分通过拿掉，但是|0，又是如何进行运算的呢，为什么能|0能达到取整的目的呢？单竖杠不是0有会是多少呢？
console.log(3|4); //7
console.log(4|4);//4
console.log(8|3);//11
console.log(5.3|4.1);//5
console.log(9|3455);//3455
其实单竖杠|就是转换为2进制之后相加得到的结果
- 3|4
转换为二进制之后011|100 相加得到111=7
- 4|4
转换为二进制之后100 |100 相加得到100=4
- 8|3
转换为二进制之后1000 |011 相加得到1011=11
JS双竖杠的作用
var objOne = undefined || 1 || null || new Date();
var objTwo = new Date();
var objThree = objOne || objTwo;
alert(objThree.toString()); //out put "1"
- JS双竖线运算符: 是或比较.如
null||'1'返回1,'2'||'1',返回2. 即或运算符中,第一个为真,后面的就不用计算了.所以得2。 - js 中 使用双竖线运算符
||,返回第一个有效值
&& 对比 ||
let firstName = null;
let lastName = null;
let nickName = "Supercoder";
// shows the first defined value:
alert(firstName ?? lastName ?? nickName ?? "Anonymous"); // Supercoder
let firstName = null;
let lastName = null;
let nickName = "Supercoder";
// shows the first truthy value:
alert(firstName || lastName || nickName || "Anonymous"); // Supercoder
The important difference between them is that:
||returns the first truthy value.??returns the first defined value.
tips: “defined” when it’s neither null nor undefined.
In other words, , || doesn’t distinguish between false, 0, an empty string "" and null/undefined. They are all the same – falsy values. If any of these is the first argument of ||, then we’ll get the second argument as the result.
