37-数据类型的转换

数据类型转换

转换为数字类型

Number()：转换为数字类型，保留小数

console.log(Number("123.45"))//123.45
console.log(Number("123.45px"));//not a number NaN
console.log(Number(true));//1
console.log(Number(false));//0
console.log(Number(undefined));//NaN
console.log(Number(null));//0

parseInt()：转换为整数，不会保留小数

console.log(parseInt("123.45"));//123
console.log(parseInt("123.45px"));//123
console.log(parseInt("123abc"));//123
console.log(parseInt("abc123"));//NaN
console.log(parseInt(true));//NaN
console.log(parseInt(false));//NaN
console.log(parseInt(undefined));//NaN
console.log(parseInt(null));//NaN

parseFloat()：转换为数字，会保留小数部分

console.log(parseFloat("123.45"));//123.45
console.log(parseFloat("123.45px"));//123.45
console.log(parseFloat(true));//NaN
console.log(parseFloat(false));//NaN
console.log(parseFloat(undefined));//NaN
console.log(parseFloat(null));//NaN

转换为字符串类型

• .toString()

  let num = 10;
  console.log(num.toString());//"10"
  

• 通过加空字符串进行隐式转换

  let num = 10; console.log(num + "");//"10"
  

转换为布尔类型

• Boolean()：转换为布尔类型

  //为false的情况
  console.log(Boolean(""));
  console.log(Boolean(0));
  console.log(Boolean(NaN));
  console.log(Boolean(undefined));
  console.log(Boolean(null));
  console.log(Boolean(false));