后端开发教程 - Java、Spring Boot 实战 - msg200.com
JavaScript 基本类型转换速查表🔥
字符串转换
布尔类型转换
数字类型转换
空类型转换
未定义类型转换
目录
类型转换可以是显式的，也可以是隐式的。
value = Number('23') // explicit
value = 5 + '25' // implicit
值类型检查
console.log(typeof value);
字符串转换
数字转字符串：
value = String(10); /* => '10' */
value = String(10 + 40); /* => '50' */
value = (10 + 40).toString(); /* => '50' */
value = new String(10 + 20); /* => '30' */
布尔值转字符串
value = String(true); /* => 'true' */
value = String(false); /* => 'false' */
数组转字符串
value = String([1, 2, 3]); /* => '1,2,3' */
value = String([ ]); /* => '' */
对象到字符串
value = String({name: "Daniel"}); /* => [object Object] */
当任何数据类型与字符串连接时，都会转换为字符串（隐式转换）：
value = 30 + ' ' + 30; /* => 30 30 */ // Space is considered a symbol.
value = 30 + '' + undefined; /* => 30undefined */
数学运算将空字符串转换为零：
value = 30 - ''; /* => 30 */
value = 30 - 'text'; /* => NaN */ // If the string is not empty, then we will get NaN - calculation error.
value = 30 - '5'; /* => 25 */ // If we write a number in a string, we will get a number type
布尔类型转换
在数学运算中，true 转换为一，false 转换为零：
value = true + 5; /* => 6 */
value = false + 5; /* => 5 */
字符串转布尔值
value = Boolean('hello'); /* => true */ // Any non-empty string will be considered true.
value = Boolean(' '); /* => true */
value = Boolean(''); /* => false */ // An empty string will be considered false.
数字转布尔值
value = Boolean(-123); /* => true */ // Any number, both positive and negative, will be considered true.
value = Boolean(123); /* => true */
value = Boolean(0); /* => false */ // Zero counts as false
未定义为布尔值
value = Boolean(undefined); /* => false */
空值转为布尔值
value = Boolean(null); /* => false */
对象转布尔值
value = Boolean({}); /* => true */ // An empty object is considered true.
数组转布尔值
value = Boolean([]); /* => true */ // An empty array is considered true.
数字类型转换
字符串转数字
value = Number('23'); /* => 23 */
value = Number('string...lalala'); /* => NaN */
value = parseInt(' 203px'); /* => 203 */ // The parseInt function reads a number from a string and removes all characters after it, but if there are characters before the number (except for a space), then it will output NaN. Serves for whole numbers.
value = parseFloat('203.212px'); /* => 203.212 */ // Works the same as parseInt, but for fractional numbers.
布尔值转数字
value = Number(true); /* => 1 */
value = Number(false); /* => 0 */
空值转为数字
value = Number(null); /* => 0 */
数组转数字
value = Number([1, 2, 3]); /* => NaN */ // NaN refers to numbers.
空类型转换
数学运算时转换为零：
value = null + 5; /* => 5 */
未定义类型转换
转换为 NaN 以进行数学运算：
value = false + undefined; /* => NaN */
感谢阅读！❤️
你也可以看看我的Redux 基础速查表