HTML5 的 canvas 元素使用 JavaScript 在网页上绘制图像。画布是一个矩形区域，您可以控制其每一像素。canvas 拥有多种绘制路径、矩形、圆形、字符以及添加图像的方法。canvas 元素本身是没有绘图能力的。所有的绘制工作必须在 JavaScript 内部完成：canvas柱状图
var arr = [

{ id: 1001, price: 100 },

{ id: 1002, price: 150 },

{ id: 1003, price: 200 },

{ id: 1004, price: 70 },

{ id: 1005, price: 300 }
];
var gap = 20;
var canvas = document.querySelector("canvas");
var ctx;
init();
function init() {

canvas.width = 400;

canvas.height = 300;

ctx = canvas.getContext("2d");

var max = arr.reduce((value, item) => {

return value < item.price ? item.price : value;

}, arr[0].price);

//max高为300的4/5,其他的高为:300*(4/5)/(max) * h maxh:240 = othersh: ? ? = 240

var scaleHeight = 300 * 4 / 5 / max;

//每个柱状图的宽为总宽-间隙宽除个数

var width = (400 - (gap * (arr.length + 1))) / arr.length;

createChart(width, scaleHeight);
}

function createChart(w, hs) {

ctx.fillStyle = "rgba(0,0,0,0.7)";

ctx.fillRect(0, 0, 400, 300);

var x = 0;

for (var i = 0; i < arr.length; i++) {

x += gap;

ctx.fillStyle = "orange";

var h = hs * arr[i].price;

ctx.fillRect(x, 300 - h, w, h);

x += w;

}
}
var arr = [

{ id: 1001, price: 100 },

{ id: 1002, price: 150 },

{ id: 1003, price: 200 },

{ id: 1004, price: 70 },

{ id: 1005, price: 300 }
];
var gap = 20;
var canvas = document.querySelector("canvas");
var ctx;
init();
function init() {

canvas.width = 400;

canvas.height = 300;

ctx = canvas.getContext("2d");

var max = arr.reduce((value, item) => {

return value < item.price ? item.price : value;

}, arr[0].price);

//max高为300的4/5,其他的高为:300*(4/5)/(max) * h maxh:240 = othersh: ? ? = 240

var scaleHeight = 300 * 4 / 5 / max;

//每个柱状图的宽为总宽-间隙宽除个数

var width = (400 - (gap * (arr.length + 1))) / arr.length;

createChart(width, scaleHeight);
}

function createChart(w, hs) {

ctx.fillStyle = "rgba(0,0,0,0.7)";

ctx.fillRect(0, 0, 400, 300);

var x = 0;

for (var i = 0; i < arr.length; i++) {

x += gap;

ctx.fillStyle = "orange";

var h = hs * arr[i].price;

ctx.fillRect(x, 300 - h, w, h);

x += w;

}
}效果：以上就是本文的全部内容，希望对大家的学习有所帮助。