请教大神，为什么x.x等于undefined y.x等于6

Question

function a(xx){

this.x = xx

return this
    
}

var x = a(5)  

var y = a(6)

console.log(x.x)  // undefined

console.log(y.x)  // 6

Answer 1

实例化对象时要用new调用构造函数。
var x = new a(5)
var y = new a(6)