目录类型转换1.String->Number2.Number->String3.混合String->Number4.String->Array5.Array-
const string = "99";
// 隐式转换
console.log(string * 1 + 77);
// 显式转换
console.log(Number(string) + 77);
const number = 66;
console.log(typeof number);
// 隐式转换
console.log(typeof (number + ""));
// 显式转换
console.log(typeof String(number));
把位于开头的数值字符串转为数值型
const string = "66.66alison";
console.log(parseInt(string));
console.log(parseFloat(string));
const name = "alison";
console.log(name.split(""));
const array = ["yooo", "alison", "ruby", "andy"];
console.log(array.join(""));
console.log(array.join("&"));
空数组为0,x单元素数组为x,多元素数组为NaN
console.log(Number([]));
console.log(Number([3]));
console.log(Number([1, 2, 3]));
主要用于将Array(由逗号隔开)、Boolean、Date、Number等对象转换成String。
const array = ["yooo", "alison", "ruby", "andy"];
console.log(array.toString());
const number = 99;
console.log(typeof number.toString());
比较和运算是两件事
在将boolean与number、string比较时,会隐式地将boolean中的true转为1、false转为0
let number = 99;
console.log(number == true);
let hd = '0';
let hd2 = "1";
let hd3 = "99";
console.log(hd == false);
console.log(hd2 == true);
console.log(hd3 == true);
在运算中string和number会被隐式转换为boolean
let number = 99;
if (number) console.log("number");
console.log(Boolean([]));
console.log(Boolean({}));
假 | 真 | |
---|---|---|
数值类型 | 0 | 其他 |
字符串类型 | 空串 | 其他 |
引用类型 | 数组和对象 |
!先将number转换为boolean类型,然后再取反
!!相当于把数值转为布尔
Boolean()
// 数值
let number = 0;
number = !!number;
console.log(Boolean(number));
// 字符串
let string = "Alison";
console.log(!!string);
console.log(Boolean(string));
// 数组
let array = [];
console.log(!!array);
console.log(Boolean(array));
// 对象
let object = {};
console.log(!!object);
console.log(Boolean(object));
// 日期
let date = new Date();
console.log(!!date);
console.log(Boolean(date));
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本文标题: Javascript类型转换详解
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