如何访问数组中对象的变量

Question

I have an array which I want to populate, every time a new startId and endID are chosen, however once I add the new object to the array, I cannot access the variables in the object, when I alert, I get undefined as a value.

This is my code;

        value = {start: this.startId, end :this.endId};

        this.array[this.array.length] = value;
        alert(this.array[this.array.length].start + " " + this.array[this.array.length].end)

I also tried this

            value = {start: this.startId, end :this.endId};

            this.array[this.array.length] = value;
            alert(this.array[this.array.length][start] + " " + this.array[this.array.length][end])

Answer 1

This won't work since you are accessing a key that is outside of the array.

Have a look at this example:

[1,2,3]// an array with the indexes 0=1, 1=2 , 2=3
.length;//3

So while you can insert a new element at arrays.length position, you cannot get one from there, as it does not exist.

So you need to access the last element at the length-1 position:

alert(this.array[this.array.length-1].start);

Sidenote:

Instead of using array[array.length] to add a new element you can make use of the push function:

this.array.push(value);