【如何理解值传递与引用传递】

如何理解值传递与引用传递
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<html>

<head>
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

	<style type="text/css">
		body {
			font-family: "Helvetica", "Arial", serif;
			color: #333;
			background-color: #ccc;
			margin: 1em 10%;
		}

		h1 {
			columns: #333;
			background-color: transparent;
		}

		a {
			color: #c60;
			background-color: transparent;
			font-weight: bold;
			text-decoration: none;
		}

		ul {
			padding: 0;
		}

		li {
			float: left;
			padding: 1em;
			list-style: none;
		}

		img {
			display: block;
			clear: both;
		}

		#imagegallery {
			list-style: none;
		}

		#imagegallery li {
			display: inline;
		}

		#imagegallery li a img {
			border: 0;
			width: 100px;
			height: 100px;
		}
	</style>
</head>

<body>
	<h1>Snapshots</h1>
	<ul id="imagegallery">
		<li>
			<a href="TestImages/53c73d41t6347a2a44ad5.jpg" title="A firewoks display">
				<img src="TestImages/53c73d41t6347a2a44ad5.jpg" alt="Fireworks">
			</a>
		</li>
		<li>
			<a href="TestImages/876591bf226b002640f252e0fecf0275.jpg" title="A cuo of black coffee">
				<img src="TestImages/876591bf226b002640f252e0fecf0275.jpg" alt="Coffee">
			</a>
		</li>
		<li>
			<a href="TestImages/Img262780588.jpg" title="A red, red rose">
				<img src="TestImages/Img262780588.jpg" alt="Rose">
			</a>
		</li>
		<li>
			<a href="TestImages/U2184P28T3D2092234F326DT20080708102538.jpg" title="The famous clock">
				<img src="TestImages/U2184P28T3D2092234F326DT20080708102538.jpg" alt="Big Ben">
			</a>
		</li>
	</ul>
	<img id="placeholder" src="TestImages/U2184P28T3D2092234F326DT20080708102538.jpg" alt="my image gallery">
	<p id="description">Choose an image.</p>
	<a href="http://www.example.com/" class="popup">Example</a>
	<script>


		function prepareGallery() {
			if (!document.getElementsByTagName) { return false }
			if (!document.getElementById) { return false }
			if (!document.getElementById("imagegallery")) { return false }
			var gallery = document.getElementById("imagegallery");
			var links = gallery.getElementsByTagName("a");
			for (var i = 0; i < links.length; i++) {
				links[i].onclick = function () {
					return showPic(this) ? false : true;
				}
			}
		}
		addLoadEvent(prepareGallery);
		function addLoadEvent(func) {
			var olaonload = window.onload;
			if (typeof window.onload != 'function') {
				window.onload = func;
			} else {
				window.onload = function () {
					olaonload();
					func();
				}
			}
		}

		function showPic(whichpic) {
			if (!document.getElementById("placeholder")) { return false }
			var source = whichpic.getAttribute("href");
			var placeholder = document.getElementById("placeholder");
			if (placeholder.nodeName != "IMG") { return false }
			placeholder.setAttribute("src", source);
			if (document.getElementById("description")) {
				var text = whichpic.getAttribute("title") ? whichpic.getAttribute("title") : "";
				var description = document.getElementById("description");
				if (description.firstChild.nodeType == 3) {
					description.firstChild.nodeValue = text;
				}
			}
			return true;
		}


		function popUp(winURL) {
			window.open(winURL, "popup", "width:320,height:480");
		}
		var links = document.getElementsByTagName("a");
		for (var i = 0; i < links.length; i++) {
			if (links[i].getAttribute("class") == "popup") {
				links[i].onclick = function () {
					popUp(this.getAttribute("href"));
					return false;
				}
			}
		}
		// function changeAgeAndReference(person) {
		// 	person.age = 25;
		// 	person = {
		// 		name: 'John',
		// 		age: 50
		// 	};

		// 	return person;
		// }
		// var personObj1 = {
		// 	name: 'Alex',
		// 	age: 30
		// };
		// var personObj2 = changeAgeAndReference(personObj1);
		// console.log(personObj1); // -> ?
		// console.log(personObj2); // -> ?
		var rotate = function (nums, k) {
			var len = nums.length;
			var newArr = nums.splice(0, len - k)
			var temp = nums.concat(newArr)
			nums = temp
			return nums;
		};
		var a = [1, 2, 3, 4, 5, 6, 7];
		rotate(a, 3);
		console.log(a);


		var a = [1, 2, 3, 4, 5, 6, 7];
		var len = a.length;
		var newArr = a;
		newArr = newArr.splice(0, len - 3);
		console.log(a);

		module.exports = {
			prepareGallery: prepareGallery
		}
	</script>
</body>

</html>
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编辑于2025-04-04