Number()是转型函数,可用于任何数据类型;

parseInt()和parseFloat()多用于将字符串转换为数值类型;

parseInt()获取整数:如果第一个字符不是数值,直接返回NaN,如果第一个字符是数值、加号、减号,则继续检测,直到字符末尾或碰到非数值字符;

parseFloat()获取小数:和parseInt()规则类似,但是parseFloat()用于获取第一个小数点前的数值,第二个小数点无效

常见Number()转换

javascript">    console.log(Number(''));//0
    console.log(Number('123'));//123
    console.log(Number('123aaa'));//NaN
    console.log(Number('aaa123'));//NaN
    console.log(Number('aaa'));//NaN
    console.log(Number(true));//1
    console.log(Number(false));//0
    console.log(Number(null));//0
    console.log(Number(undefined));//NaN

常见的parseInt()转换

javascript">    console.log(parseInt(''));//NaN
    console.log(parseInt('123'));//123
    console.log(parseInt('0123'));//123
    console.log(parseInt('+123'));//123
    console.log(parseInt('123.45'));//123
    console.log(parseInt('123aaa'));//123
    console.log(parseInt('aaa123'));//NaN
    console.log(parseInt('aaa'));//NaN
    console.log(parseInt(true));//NaN
    console.log(parseInt(false));//NaN
    console.log(parseInt(null));//NaN
    console.log(parseInt(undefined));//NaN

常见的parseFloat()转换

javascript">    console.log(parseFloat(''));//NaN
    console.log(parseFloat('123'));//123
    console.log(parseFloat('+123'));//123
    console.log(parseFloat('0123'));//123
    console.log(parseFloat('123.45'));//123.45
    console.log(parseFloat('123.45.67'));//123.45
    console.log(parseFloat('123aaa'));//123
    console.log(parseFloat('aaa123'));//NaN
    console.log(parseFloat('aaa'));//NaN
    console.log(parseFloat(true));//NaN
    console.log(parseFloat(false));//NaN
    console.log(parseFloat(null));//NaN
    console.log(parseFloat(undefined));//NaN