Question

Below are is a snippet of code containing object constructor and a function to populate an array of said objects. The populate function uses AJAX get() to consume data from a text file into an array. The array can be accessed and used from within the scope of the function; but my question is how can I use this array outside of the scope of the function? I have tried "initializing" the array globally and return the array from the function, which should be filled with objects. However, the array is empty when I try using it outside of the function's scope. This is odd to me because I am used to programming in C++. Any help would be greatly appreciated.

<script>
var file = "names.txt";

// object constructor
function person(first, middle, last) {
    this.f_name = first;
    this.m_name = middle;
    this.l_name = last;
}

// populate object array
function populate() {
    var people = [{}];
    $.get(file, function(txt){
        var records = txt.split("\n");
        for(var i = 0; i < records.length; i++) {
            var row = records[i].split("\t");
            people[i] = new person(
                row[0],
                row[1],
                row[2]
            );
        }
    });
    return people;
}

var arr = [{}];
arr = populate();
console.log(arr);              //LOG: [object Object]
console.log(arr[666]);         //LOG: undefined
console.log(arr[666].f_name);  //SCRIPT5007: Unable to get
                               //  value of the property
                               //  'f_name': object is null
                               //  or undefined 



</script>

Answer 1

arr = populate(); //this is called and $.get would have not finished the execution. $.get is as asynchronous call.

but the console.log statements will be executed before the arr is filled.

Use success call function to do post implementation of success .

function populate() {
    var people = [{}];
    $.get(file, function(txt){
        var records = txt.split("\n");
        for(var i = 0; i < records.length; i++) {
            var row = records[i].split("\t");
            people[i] = new person(
                row[0],
                row[1],
                row[2]
            );
        }

    });
    console.log(people);              //LOG: [object Object]
    console.log(people[666]);         //LOG: undefined
    console.log(people[666].f_name);
}

AJAX Array Object Construction Out of Scope Error

1 个答案: