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How do you detect collisions between jQuery `` elements?

Mary-Kate OlsenOriginal: 2024-11-12 17:26:02939browse

Collision Detection between jQuery Div Elements

Detecting collisions between elements is a fundamental task in many web applications. In this case, the objective is to determine if two specific

elements, represented as colored boxes, have collided while moving perpendicularly to each other.

One effective approach to tackle this problem is to leverage the overlaps function provided below:

var overlaps = (function () {
    function getPositions( elem ) {
        var pos, width, height;
        pos = $( elem ).position();
        width = $( elem ).width();
        height = $( elem ).height();
        return [ [ pos.left, pos.left + width ], [ pos.top, pos.top + height ] ];
    }

    function comparePositions( p1, p2 ) {
        var r1, r2;
        r1 = p1[0] < p2[0] ? p1 : p2;
        r2 = p1[0] < p2[0] ? p2 : p1;
        return r1[1] > r2[0] || r1[0] === r2[0];
    }

    return function ( a, b ) {
        var pos1 = getPositions( a ),
            pos2 = getPositions( b );
        return comparePositions( pos1[0], pos2[0] ) && comparePositions( pos1[1], pos2[1] );
    };
})();

This function takes two

elements as parameters and returns a boolean value indicating whether they overlap based on their positions and dimensions. The function first retrieves the position and size of each element and then compares their ranges along the x-axis and y-axis. It returns true if there is an overlap in either direction.

To demonstrate the usage of this function, you can create a set of

elements in your HTML document, style them as boxes, and assign them unique IDs for identification. Then, within a jQuery script, you can invoke the overlaps function to check for collisions between these boxes. The following code provides an example:

$(function () {
    var area = $( '#area' )[0],
        box = $( '#box0' )[0],
        html;
    
    html = $( area ).children().not( box ).map( function ( i ) {
        return '<p>Red box + Box ' + ( i + 1 ) + ' = ' + overlaps( box, this ) + '</p>';
    }).get().join( '' );

    $( 'body' ).append( html );
});

In this example, a red box named "Red box" is created and moved around using the mouse. Several other boxes labeled "Box 1" to "Box 4" are positioned at different locations in the "area" div. The jQuery script checks for collisions between the "Red box" and each of the other boxes and displays the results in a series of

elements.

By utilizing the overlaps function, you can effectively implement collision detection for jQuery

elements, enabling dynamic interactions and real-time collision handling in your web applications.

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