从数组中检索的var是未定义的？

Question

下面的代码包含一个名为buttonColours的数组,一个0到3的随机数,然后randomColour应该是buttonColours数组中的一个随机颜色,但事实并非如此.它将randomColour归类为undefined.

var buttonColours = ["blue", "red", "green"];
var randomNumber = Math.floor(Math.random * 3);
var randomColour = buttonColours[randomNumber];
console.log(randomColour);

console.log仅将randomColor记录为undefined.有原因吗？

Answer 1

如果你在每一行上都有一个console.log,你就会直接知道这个问题:

var buttonColours = ["blue", "red", "green"];
console.log(buttonColours); // ["blue", "red", "green"]
var randomNumber = Math.floor(Math.random * 3);
console.log(randomNumber); // NaN
var randomColour = buttonColours[randomNumber];
console.log(randomColour); // undefined

问题是你Math.floor(Math.random * 3)应该回归NaNMath.random()

var buttonColours = ["blue", "red", "green"];
var randomNumber = Math.floor(Math.random() * 3);
var randomColour = buttonColours[randomNumber];
console.log(randomColour);