canvas绘制随机颜色的柱形图

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
body{
text-align: center;
}
canvas{
background: #ddd;
}
</style>
</head>
<body>
<canvas id="canvas" width="800" height="700"></canvas>
<script src="jquery-3.2.1.js"></script>
<script>
//获取画笔工具
//创建变量保存画布宽度高度边界距离
//绘制统计图的轮廓
//发送ajax请求数据
//返回数据,动态绘制图形 var elem = document.getElementById("canvas");
var canvas = elem.getContext("2d");
var w= 800,//画布宽度
h = 700,//画布高度
pd = 50 ;//统计图的内容到画布边界的距离
canvas.strokeRect(pd,pd,w-2*pd,h-2*pd);
$.ajax({
type:"GET",
url:"saledata.php",
success:function(data){
console.log("成功接收数据");
console.log(data);
//数据个数
//每个柱子/间距宽度
var count = data.length;
var barWidth = (w-2*pd)/(2*count+1);
for(var i = 0;i<count;i++){
var d = data[i];//第i月份的数量
//柱子的宽度
var bw = barWidth;
//柱子的高度
var bh = d.value;
//柱子的x
var bx = pd +(2*i+1)*barWidth;
//柱子的y
var by = h-pd-bh;
//绘制矩形
//canvas.strokeRect(bx,by,bw,bh);
canvas.fillStyle = rColor();
canvas.fillRect(bx,by,bw,bh);
}
},
error:function(){
alert("网络出现故障,请检查!");
}
});
function rColor(){
var r = Math.floor(Math.random()*256);
var g = Math.floor(Math.random()*256);
var b = Math.floor(Math.random()*256);
return `rgb(${r},${g},${b})`;
}
</script>
</body>
</html>
<?php
header("Content-Type:application/json;charset=utf-8");
$rows = [];
/*
$rows=[
["月份"=>"一月","value"=>280],
["月份"=>"二月","value"=>270],
["月份"=>"三月","value"=>380],
["月份"=>"四月","value"=>280],
["月份"=>"五月","value"=>280],
["月份"=>"六月","value"=>210],
["月份"=>"七月","value"=>180],
["月份"=>"八月","value"=>280],
["月份"=>"九月","value"=>200],
["月份"=>"十月","value"=>280],
["月份"=>"十一月","value"=>300],
["月份"=>"十二月","value"=>300]
];
*/
$rows[]=["月份"=>"1月","value"=>160];
$rows[]=["月份"=>"2月","value"=>290];
$rows[]=["月份"=>"3月","value"=>220];
$rows[]=["月份"=>"4月","value"=>100];
$rows[]=["月份"=>"5月","value"=>190];
$rows[]=["月份"=>"6月","value"=>170];
$rows[]=["月份"=>"7月","value"=>270];
$rows[]=["月份"=>"8月","value"=>120];
$rows[]=["月份"=>"9月","value"=>250];
$rows[]=["月份"=>"10月","value"=>240];
$rows[]=["月份"=>"11月","value"=>230];
$rows[]=["月份"=>"12月","value"=>210]; echo json_encode($rows);
?>

***********记得添加jquery-3.2.1.js哦

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