javascript - Please show me a more elegant way to do this -

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to me, obvious way this: given start point , end point, tell me if end point / down / left / upleft / downright... etc of start point. heres core of logic :

function getsector() {     var y = starty - endy;     var x = startx - endx;     var angle = math.atan2(y,x) * 57.29578;//~57 deg per radian     //atan2(y,x) returns num between -pi , pi, represents angle in radians     console.log("angle:" + angle);     if( (angle > -22.5) && (angle < 22.5) ) attackdir = "left";     if( (angle > 22.5) && (angle < 67.5) ) attackdir = "upleft";     if( (angle > 67.5) && (angle < 112.5) ) attackdir = "up";     if( (angle > 112.5) && (angle < 157.5) ) attackdir = "upright";     if( (angle > 157.5) && (angle <= 180) ) attackdir = "right";     if( (angle > -179) && (angle <= -157) ) attackdir = "right";     if( (angle > -157) && (angle < -112.5) ) attackdir = "downright";     if( (angle > -112.5) && (angle < -67.5) ) attackdir = "down";     if( (angle > -67.5) && (angle < -22.5) ) attackdir = "downleft";     console.log("attackdir:" + attackdir); }

i'm interested in seeing better way, more so, how arrived @ way.

i guess key of sorts in order : left = 0 = 90 right = 179 or -179 (down negative mirror of up) down = -90

when doing bounds checking, it's more readable if create function named between(min, val, max);

function between(min, val, max) {  return (val > min) && (val < max); }

in addition, can test right/left, , after test down/up.. while appending string. logic cut down 4 if statements.

var final=""; if(/*isup*/) final="up" else if(/*isdown*/) final="down"  if(/*isright*/) final+= "right"; else if(/*isleft*/) final += "left";

edit: stated stefan, 57.29578 magical number. didn't realize meant 180/(math.pi)... stated, "optimization" you're making makes code illegible, , performance gain moot.

you should check u/d/l/r x/y position relative origin, not angles.


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