javascript - How to make a border? -

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i have element

<div id="square"></div>

he has property move on document

var square = document.getelementbyid("square");     document.body.onkeydown = function(e) {     if (e.keycode == 37) {left()}     if (e.keycode == 38) {up()}     if (e.keycode == 39) {right()}     if (e.keycode == 40) {down()} }

how make function, not allowed movement, if square element closest document border? jsfiddle: https://jsfiddle.net/zutxylsq/

you need check if left outside of boundaries this:

function left() {     console.log('left');     var left = parseint(square.style.left || getcomputedstyle(square)['left'], 10);     if (left >= 50) {         square.style.left = (left - 50) + 'px';     } } function right() {     console.log('right');     var left = parseint(square.style.left || getcomputedstyle(square)['left'], 10);     if (left+50+square.offsetwidth < window.innerwidth) {         square.style.left = (left + 50) + 'px';     } }

https://jsfiddle.net/zutxylsq/3/

and same , down.


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