Edit in JSFiddle

var str = "          Hello World!         ";
var res = str.trim(); // 공백 제거 Hello World!

// 출력
function reset() {
	document.getElementById("pre").innerHTML = str;
};

function trimHandle() {
	document.getElementById("pre").innerHTML = res;
}

window.onload = function() {
	reset();
}

<pre id="pre"></pre>
<button type="button" onclick="trimHandle()">trim</button>
<button type="button" onclick="reset()">reset</button>