第一种方法数值转换为字符串 var s1 = 12; 数值 var n = s1.toString(); 转换为字符串类型 console.log(typeof n); 用typeof来打印数据类型 第二种方法数值转换为字符串 var s1=12; console.log(typeof String(s1)); 第三种方法数值转换为字符串 var s2=''+1; console.log(typeof s2); 布尔值转换为字符串 var n=true; var s1=n.toString(); console.log(typeof s1); 其他类型转换为数值 var s = Number('c'); 字符串转为数值 console.log(s); console.log(typeof s); 结果是NaN 数据类型是数值类型number var s = Number('1'); console.log(s); console.log(typeof s); 结果是数值类型1 由字符串转换为数值类型 var s = Number(null); console.log(s); console.log(typeof s); 结果是0 由字符串转换为数值类型 var s = Number(undefined); console.log(s); console.log(typeof s); 结果是NaN 数据类型是数值类型number var s=parseInt('1'); var s1=parseInt('1q1'); var s2=parseInt(null); var s3=parseInt(undefined); console.log(s,s1,s2,s3); console.log(typeof s); console.log(typeof s1); console.log(typeof s2); console.log(typeof s3); 结果: 1 1 NaN NaN typeof结果:number number number number var s=parseFloat('1'); var s1=parseFloat('1q1'); var s2=parseFloat(null); var s3=parseFloat(undefined); var s4=parseFloat('1.23.4'); console.log(s,s1,s2,s3,s4); console.log(typeof s); console.log(typeof s1); console.log(typeof s2); console.log(typeof s3); console.log(typeof s4); 结果: 1 1 NaN NaN 1.23 typeof结果:number number number number number 布尔类型转换 var s = Boolean(0); var s1 = Boolean("0"); var s2 = Boolean(null); var s3 = Boolean(undefined); var s4 = Boolean(""); var s5 = Boolean(" "); console.log(s,s1,s2,s3,s4,s5); 结果:false true false false false true |