has-intersection

Return true if two line segments have intersection.

Install

npm install has-intersection

Usage

//          [x , y, x', y'] 
var lineA = [-5, 5, 5,-5];
var lineB = [ 5, 5,-5,-5]
if(hasIntersection(lineA, lineB)){
    console.log("They have!");
}

Code

module.exports = hasIntersection =function(lineA,lineB) {
    var x1 = lineA[0];
    var y1 = lineA[1];
    var f1 = lineA[2] - lineA[0];
    var g1 = lineA[3] - lineA[1];

    var x2 = lineB[0];
    var y2 = lineB[1];
    var f2 = lineB[2] - lineB[0];
    var g2 = lineB[3] - lineB[1];

    var det = f2 * g1 - f1 * g2;
    if (det == 0) {
        return false;
    }
    var dx = x2 - x1;
    var dy = y2 - y1;
    var t1 = (f2*dy - g2*dx)/det;
    var t2 = (f1*dy - g1*dx)/det;
    if (t1 > 0 && t1 < 1 && t2 > 0 && t2 < 1){
        return {x : x1 + f1*t1, y : y1 + g1*t1};
    }else{
        return false;
    }
};