console 中的格式化打印（占位符），和样式定义

格式化打印

Gecko 9.0 (Firefox 9.0 / Thunderbird 9.0 / SeaMonkey 2.6) 首次发布对string substitutions的支持.你能够在传递给console的方法的时候使用下面的字符以期进行参数的替换。

Substitution string	Description
%o	打印javascript对象，能够是整数、字符串以及JSON数据
%d or %i	打印整数
%s	打印字符串
%f	打印浮点数

当要替换的参数类型和预期的打印类型不一样时，参数会被转换成预期的打印类型。

for (var i=0; i<5; i++) {
  console.log("Hello, %s. You've called me %d times.", "Bob", i+1);
}
console.log("I want to print a number:%d","string")

 

输出样例以下所示：

[13:14:13.481] Hello, Bob. You've called me 1 times.
[13:14:13.483] Hello, Bob. You've called me 2 times.
[13:14:13.485] Hello, Bob. You've called me 3 times.
[13:14:13.487] Hello, Bob. You've called me 4 times.
[13:14:13.488] Hello, Bob. You've called me 5 times.
[13:14:13.489] I want to print a number:NaN

 

咱们发现"string"字符串被转换成数字失败成转换成 [NaN en-US]

为console定义样式

你能够使用"%c"为打印内容定义样式:

console.log("%cMy stylish message", "color: red; font-style: italic");