javascript学习笔记（一）

JavaScript，是弱类型的语言；

六种数据类型：string，Number，Boolean，Null，Undefined，Ojbect（Function、Array、Date、...）

隐形转换：

“+”  “-”

var x = "This is the answer " + 47;
var y = 47 + " is the answer";
console.log(x); //This is the answer 47
console.log(y); //47 is the answer

var num = "37" + 7; 
var num2 = "37" - 7;
console.log(num); //377
console.log(num2); //30

“==”

console.log("1.23" == 1.23);
console.log(0 == false);
console.log(null == undefined);
console.log(new Object() == new Object());
console.log([1, 2] == [1, 2]);

 

“===”

a===b

类型不同，返回false；

类型相同：

console.log(null===null);
console.log(undefined===undefined);
console.log(NaN===NaN);