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javascriptassociative-array

Javascript and associative arrays

I am new to JS so I am trying to use the associative arrays and am getting an error when I run the following JS code.

Uncaught TypeError: Cannot set properties of undefined (setting 'x')

Any assist would be great.

var activeField;

fields = []; //  holds all the defined fields

function Field() {
  this.polypoints = [{}];
}

var field = new Field();
var Points;

fields.push(field);

activeField = (fields.length) - 1;
Points = fields[activeField].polypoints.length;
Points = Points + 1;
fields[activeField].polypoints[Points].x = 1;
fields[activeField].polypoints[Points].y = 1;

console.log("values in array:", activeField, polyPoints, fields);

Solution

  • When you make Points=Points+1;, Points is now 1. fields[activeField].polypoints[Points] is undefined b/c you haven't created an object. The object is at fields[activeField].polypoints[0] instead. To add object, you have to create.

    fields[activeField].polypoints[Points]={x:1,y:1}