JS实现网站添加好看的背景彩带

动态演示效果如图所示

代码

<script>
	(function(name, factory) {
		if (typeof window === "object") {
			window[name] = factory()
		}
	})("Ribbons", function() {
		var _w = window,
			_b = document.body,
			_d = document.documentElement;
		var random = function() {
				if (arguments.length === 1) {
					if (Array.isArray(arguments[0])) {
						var index = Math.round(random(0, arguments[0].length - 1));
						return arguments[0][index]
					}
					return random(0, arguments[0])
				} else if (arguments.length === 2) {
					return Math.random() * (arguments[1] - arguments[0]) + arguments[0]
				}
				return 0
			};
		var screenInfo = function(e) {
				var width = Math.max(0, _w.innerWidth || _d.clientWidth || _b.clientWidth || 0),
					height = Math.max(0, _w.innerHeight || _d.clientHeight || _b.clientHeight || 0),
					scrollx = Math.max(0, _w.pageXOffset || _d.scrollLeft || _b.scrollLeft || 0) - (_d.clientLeft || 0),
					scrolly = Math.max(0, _w.pageYOffset || _d.scrollTop || _b.scrollTop || 0) - (_d.clientTop || 0);
				return {
					width: width,
					height: height,
					ratio: width / height,
					centerx: width / 2,
					centery: height / 2,
					scrollx: scrollx,
					scrolly: scrolly
				}
			};
		var mouseInfo = function(e) {
				var screen = screenInfo(e),
					mousex = e ? Math.max(0, e.pageX || e.clientX || 0) : 0,
					mousey = e ? Math.max(0, e.pageY || e.clientY || 0) : 0;
				return {
					mousex: mousex,
					mousey: mousey,
					centerx: mousex - screen.width / 2,
					centery: mousey - screen.height / 2
				}
			};
		var Point = function(x, y) {
				this.x = 0;
				this.y = 0;
				this.set(x, y)
			};
		Point.prototype = {
			constructor: Point,
			set: function(x, y) {
				this.x = x || 0;
				this.y = y || 0
			},
			copy: function(point) {
				this.x = point.x || 0;
				this.y = point.y || 0;
				return this
			},
			multiply: function(x, y) {
				this.x *= x || 1;
				this.y *= y || 1;
				return this
			},
			divide: function(x, y) {
				this.x /= x || 1;
				this.y /= y || 1;
				return this
			},
			add: function(x, y) {
				this.x += x || 0;
				this.y += y || 0;
				return this
			},
			subtract: function(x, y) {
				this.x -= x || 0;
				this.y -= y || 0;
				return this
			},
			clampX: function(min, max) {
				this.x = Math.max(min, Math.min(this.x, max));
				return this
			},
			clampY: function(min, max) {
				this.y = Math.max(min, Math.min(this.y, max));
				return this
			},
			flipX: function() {
				this.x *= -1;
				return this
			},
			flipY: function() {
				this.y *= -1;
				return this
			}
		};
		var Factory = function(options) {
				this._canvas = null;
				this._context = null;
				this._sto = null;
				this._width = 0;
				this._height = 0;
				this._scroll = 0;
				this._ribbons = [];
				this._options = {
					colorSaturation: "80%",
					colorBrightness: "60%",
					colorAlpha: 0.65,
					colorCycleSpeed: 6,
					verticalPosition: "center",
					horizontalSpeed: 150,
					ribbonCount: 5,
					strokeSize: 5,
					parallaxAmount: -0.5,
					animateSections: true
				};
				this._onDraw = this._onDraw.bind(this);
				this._onResize = this._onResize.bind(this);
				this._onScroll = this._onScroll.bind(this);
				this.setOptions(options);
				this.init()
			};
		Factory.prototype = {
			constructor: Factory,
			setOptions: function(options) {
				if (typeof options === "object") {
					for (var key in options) {
						if (options.hasOwnProperty(key)) {
							this._options[key] = options[key]
						}
					}
				}
			},
			init: function() {
				try {
					this._canvas = document.createElement("canvas");
					this._canvas.style["display"] = "block";
					this._canvas.style["position"] = "fixed";
					this._canvas.style["margin"] = "0";
					this._canvas.style["padding"] = "0";
					this._canvas.style["border"] = "0";
					this._canvas.style["outline"] = "0";
					this._canvas.style["left"] = "0";
					this._canvas.style["top"] = "0";
					this._canvas.style["width"] = "100%";
					this._canvas.style["height"] = "100%";
					this._canvas.style["z-index"] = "-1";
					this._onResize();
					this._context = this._canvas.getContext("2d");
					this._context.clearRect(0, 0, this._width, this._height);
					this._context.globalAlpha = this._options.colorAlpha;
					window.addEventListener("resize", this._onResize);
					window.addEventListener("scroll", this._onScroll);
					document.body.appendChild(this._canvas)
				} catch (e) {
					console.warn("Canvas Context Error: " + e.toString());
					return
				}
				this._onDraw()
			},
			addRibbon: function() {
				var dir = Math.round(random(1, 9)) > 5 ? "right" : "left",
					stop = 1000,
					hide = 200,
					min = 0 - hide,
					max = this._width + hide,
					movex = 0,
					movey = 0,
					startx = dir === "right" ? min : max,
					starty = Math.round(random(0, this._height));
				if (/^(top|min)$/i.test(this._options.verticalPosition)) {
					starty = 0 + hide
				} else if (/^(middle|center)$/i.test(this._options.verticalPosition)) {
					starty = this._height / 2
				} else if (/^(bottom|max)$/i.test(this._options.verticalPosition)) {
					starty = this._height - hide
				}
				var ribbon = [],
					point1 = new Point(startx, starty),
					point2 = new Point(startx, starty),
					point3 = null,
					color = Math.round(random(0, 360)),
					delay = 0;
				while (true) {
					if (stop <= 0) break;
					stop--;
					movex = Math.round((Math.random() * 1 - 0.2) * this._options.horizontalSpeed);
					movey = Math.round((Math.random() * 1 - 0.5) * (this._height * 0.25));
					point3 = new Point();
					point3.copy(point2);
					if (dir === "right") {
						point3.add(movex, movey);
						if (point2.x >= max) break
					} else if (dir === "left") {
						point3.subtract(movex, movey);
						if (point2.x <= min) break
					}
					ribbon.push({
						point1: new Point(point1.x, point1.y),
						point2: new Point(point2.x, point2.y),
						point3: point3,
						color: color,
						delay: delay,
						dir: dir,
						alpha: 0,
						phase: 0
					});
					point1.copy(point2);
					point2.copy(point3);
					delay += 4;
					color += this._options.colorCycleSpeed
				}
				this._ribbons.push(ribbon)
			},
			_drawRibbonSection: function(section) {
				if (section) {
					if (section.phase >= 1 && section.alpha <= 0) {
						return true
					}
					if (section.delay <= 0) {
						section.phase += 0.02;
						section.alpha = Math.sin(section.phase) * 1;
						section.alpha = section.alpha <= 0 ? 0 : section.alpha;
						section.alpha = section.alpha >= 1 ? 1 : section.alpha;
						if (this._options.animateSections) {
							var mod = Math.sin(1 + section.phase * Math.PI / 2) * 0.1;
							if (section.dir === "right") {
								section.point1.add(mod, 0);
								section.point2.add(mod, 0);
								section.point3.add(mod, 0)
							} else {
								section.point1.subtract(mod, 0);
								section.point2.subtract(mod, 0);
								section.point3.subtract(mod, 0)
							}
							section.point1.add(0, mod);
							section.point2.add(0, mod);
							section.point3.add(0, mod)
						}
					} else {
						section.delay -= 0.5
					}
					var s = this._options.colorSaturation,
						l = this._options.colorBrightness,
						c = "hsla(" + section.color + ", " + s + ", " + l + ", " + section.alpha + " )";
					this._context.save();
					if (this._options.parallaxAmount !== 0) {
						this._context.translate(0, this._scroll * this._options.parallaxAmount)
					}
					this._context.beginPath();
					this._context.moveTo(section.point1.x, section.point1.y);
					this._context.lineTo(section.point2.x, section.point2.y);
					this._context.lineTo(section.point3.x, section.point3.y);
					this._context.fillStyle = c;
					this._context.fill();
					if (this._options.strokeSize > 0) {
						this._context.lineWidth = this._options.strokeSize;
						this._context.strokeStyle = c;
						this._context.lineCap = "round";
						this._context.stroke()
					}
					this._context.restore()
				}
				return false
			},
			_onDraw: function() {
				for (var i = 0, t = this._ribbons.length; i < t; ++i) {
					if (!this._ribbons[i]) {
						this._ribbons.splice(i, 1)
					}
				}
				this._context.clearRect(0, 0, this._width, this._height);
				for (var a = 0; a < this._ribbons.length; ++a) {
					var ribbon = this._ribbons[a],
						numSections = ribbon.length,
						numDone = 0;
					for (var b = 0; b < numSections; ++b) {
						if (this._drawRibbonSection(ribbon[b])) {
							numDone++
						}
					}
					if (numDone >= numSections) {
						this._ribbons[a] = null
					}
				}
				if (this._ribbons.length < this._options.ribbonCount) {
					this.addRibbon()
				}
				requestAnimationFrame(this._onDraw)
			},
			_onResize: function(e) {
				var screen = screenInfo(e);
				this._width = screen.width;
				this._height = screen.height;
				if (this._canvas) {
					this._canvas.width = this._width;
					this._canvas.height = this._height;
					if (this._context) {
						this._context.globalAlpha = this._options.colorAlpha
					}
				}
			},
			_onScroll: function(e) {
				var screen = screenInfo(e);
				this._scroll = screen.scrolly
			}
		};
		return Factory
	});
	new Ribbons({
		colorSaturation: "60%",
		colorBrightness: "50%",
		colorAlpha: 0.5,
		colorCycleSpeed: 5,
		verticalPosition: "random",
		horizontalSpeed: 200,
		ribbonCount: 3,
		strokeSize: 0,
		parallaxAmount: -0.2,
		animateSections: true
	});
</script>
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