Javascript For Loop为事件侦听器触发而减慢进度
我正在尝试根据上传的进度更改元素背景颜色。我遇到的问题是,与启动的progress事件侦听器相比,for循环的速度要慢得多。我能做些什么吗Javascript For Loop为事件侦听器触发而减慢进度,javascript,for-loop,upload,progress,xmlhttprequest-level2,Javascript,For Loop,Upload,Progress,Xmlhttprequest Level2,我正在尝试根据上传的进度更改元素背景颜色。我遇到的问题是,与启动的progress事件侦听器相比,for循环的速度要慢得多。我能做些什么吗 var colors = [ "#fff2f2", "#ffe6e6", "#ffd9d9", "#ffcccc", "#ffbfbf", "#ffb3b3", "#ff9999", "#ff7373", "#ff8080", "#ff5959", "#ff4d4d", "#ff4040", "#ff3333", "#ff2626", "#ff191
var colors = [
"#fff2f2",
"#ffe6e6",
"#ffd9d9",
"#ffcccc",
"#ffbfbf",
"#ffb3b3",
"#ff9999",
"#ff7373",
"#ff8080",
"#ff5959",
"#ff4d4d",
"#ff4040",
"#ff3333",
"#ff2626",
"#ff1919",
"#ff0d0d",
"#ff0000",
]
var first = 0;
var last = 5;
var xhr = new XMLHttpRequest();
xhr.upload.addEventListener("progress", updateProgress, false);
var foo = document.getElementById("uploadScreen");
var form = document.getElementById("uploadForm");
var percentComplete;
xhr.open("POST", "php/upload.php", true);
xhr.send(new FormData(form));
function updateProgress(event) {
if (event.lengthComputable) {
percentComplete = Math.round(event.loaded / event.total * 100);
for (i=0; i < colors.length; i++) {
if (percentComplete > first && percentComplete < last ) {
console.log(foo.style.backgroundColor = colors[i]);
break;
}
}
first = first +5;
last = last +5;
} else {
alert("no no");
}
}
var颜色=[
“#fff2f2”,
“#ffe6e6”,
“#ffd9d9”,
“#ffcccc”,
“#ffbfbf”,
“#ffb3b3”,
“#ff9999”,
“#ff7373”,
“#ff8080”,
“#ff5959”,
“#ff4d”,
“#ff4040”,
“#ff3333”,
“#ff2626”,
“#ff1919”,
“#ff0d0d”,
“#ff0000”,
]
var first=0;
var last=5;
var xhr=new XMLHttpRequest();
addEventListener(“progress”,updateProgress,false);
var foo=document.getElementById(“uploadScreen”);
var form=document.getElementById(“uploadForm”);
var完成百分比;
open(“POST”,“php/upload.php”,true);
xhr.send(新表单数据(表单));
函数updateProgress(事件){
if(事件长度可计算){
完成百分比=数学轮(event.loaded/event.total*100);
对于(i=0;i第一个和完成百分比<最后一个){
log(foo.style.backgroundColor=colors[i]);
打破
}
}
第一个=第一个+5;
last=last+5;
}否则{
警告(“否”);
}
}
不要将整数作为百分比,而是将其作为介于0和1之间的值。然后将它乘以数组的长度,得到正确的索引
var percentComplete = event.loaded / event.total;
var index = Math.round(percentComplete * (colors.length - 1)); // Subtract 1 to account for zero based indexing
foo.style.backgroundColor = colors[index];
不要将整数作为百分比,而是将其作为介于0和1之间的值。然后将它乘以数组的长度,得到正确的索引
var percentComplete = event.loaded / event.total;
var index = Math.round(percentComplete * (colors.length - 1)); // Subtract 1 to account for zero based indexing
foo.style.backgroundColor = colors[index];
我认为在这种情况下没有必要使用for循环
我认为在这种情况下没有必要使用for循环。for循环在每次迭代中都进行精确比较的点是什么?for循环在每次迭代中都进行精确比较的点是什么?哇,这是一个很棒的数学公式!非常感谢你!我从来没有想过会这样。哇,这是一个很棒的数学公式!非常感谢你!我从没想过会这样。