Check to see if coordinates are in jQuery array using inArray()

Question

I'm mapping some points as dots onto a canvas, and I want dots which are repeats to be rendered as larger dots.

I need to check to see if the coordinate has already been mapped before, so I want to store the coordinates in an array as I go.

Here's what I have. I'm unsure about the .inArray line. How do I check to see if the coordinate is already in the array?

$(function() {
  var arr = [];
  arr.push([0,1]);
  arr.push([2,1]);
  arr.push([3,1]);
  arr.push([4,1]);
  arr.push([5,1]);

  if(jQuery.inArray("2,1",arr)) {
    alert("not there");
  }

});

HERE'S A SIMPLIFIED FIDDLE.

Does your code work or not work? If it doesn't work, what are the errors or problems that you are encountering? — Lee Taylor
– Lee Taylor, Commented Jan 15, 2013 at 20:57
How accurate (to how many decimal places) are those coordinates? You might just need to round them off using toFixed before pushing them onto your coordinates array. — Blazemonger
– Blazemonger, Commented Jan 15, 2013 at 20:59
It does not work. And I'm pretty sure the coordinates are floating point values. They're coming from Twitter tweet data. It'd be ideal if the coordinates "matched" if they were +/- a few coordinate degrees. I posted a Fiddle. — Jon
– Jon, Commented Jan 15, 2013 at 21:00

Matanya · Accepted Answer · 2013-01-15 22:22:57Z

2

As far as I know, inArray only tests for simple values (i.e. not arrays or objects). You can use filter instead: Fiddle

 var arr = [];
  arr.push([0,1]);
  arr.push([2,1]);
  arr.push([3,1]);
  arr.push([4,1]);
  arr.push([5,1]);

x=2;
y=1;
    var filtered = $(arr).filter(function(){
        thisX = this[0];
        thisY= this[1];
        return x==thisX && y==thisY; 
    });
    if(filtered.length > 0){
       alert("yes"); 
    }
    else {
      alert("no");
    }

To test for range change the return condition like so:

return (x>thisX-0.5 && x<thisX+0.5) && (y>thisY-0.5 && y<thisY+0.5);

edited Jan 15, 2013 at 22:22

answered Jan 15, 2013 at 21:15

Matanya

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3 Comments

Jon Over a year ago

This seems to work best. How can I alter this to check if the values are within +/- 2 coordinate degrees? So if [1.5,2,0] is stored, then with +/- 0.5 [1.1, 1.8] would match?

Alexander Over a year ago

You should not use .filter() in non-jQuery objects

Jon Over a year ago

Is there an alternative, Alex?

Community · Accepted Answer · 2017-05-23 11:43:08Z

0

After debugging your fiddle, it appears the problem has to do with how JavaScript tests for equality -- two arrays of the same length with identical elements in the identical order are still not considered "strictly equal" (===).

To work around this, you'll have to develop your own function for testing equality.

edited May 23, 2017 at 11:43

CommunityBot

11 silver badge

answered Jan 15, 2013 at 21:11

Blazemonger

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