Javascript 如何在上传前预览多张图片？
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时间：2020-08-23 22:34:18 来源:igfitidea点击:
How to preview multiple images before upload?
提问by silvercity
I have a page with four images for the user to select. I want the user to be able to preview each image on the site before upload.
我有一个包含四个图像的页面供用户选择。我希望用户能够在上传之前预览网站上的每个图像。
The JavaScript code below works for only one image but I would like it to work for multiple images uploaded via <input type="file">.
下面的 JavaScript 代码仅适用于一张图片，但我希望它适用于通过<input type="file">.
What will be the best way to do this?
什么是最好的方法来做到这一点？
function readURL(input) {
if (input.files && input.files[0]) {
var reader = new FileReader();
reader.onload = function (e) {
$('#output').attr('src', e.target.result);
}
reader.readAsDataURL(input.files[0]);
}
}
$("#file-input").change(function () {
readURL(this);
});
回答by Artem Solovev
Here is jQueryversion for you. I think it more simplest thing.
这是给你的jQuery版本。我认为它更简单的事情。
$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery"></div>回答by Roko C. Buljan
Add the multipleattribute to your inputelement.
将multiple属性添加到您的input元素。
Javascript
Javascript
function previewImages() {
var preview = document.querySelector('#preview');
if (this.files) {
[].forEach.call(this.files, readAndPreview);
}
function readAndPreview(file) {
// Make sure `file.name` matches our extensions criteria
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
return alert(file.name + " is not an image");
} // else...
var reader = new FileReader();
reader.addEventListener("load", function() {
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = this.result;
preview.appendChild(image);
});
reader.readAsDataURL(file);
}
}
document.querySelector('#file-input').addEventListener("change", previewImages);<input id="file-input" type="file" multiple>
<div id="preview"></div>jQuery adaptation:
jQuery 适配：
function previewImages() {
var $preview = $('#preview').empty();
if (this.files) $.each(this.files, readAndPreview);
function readAndPreview(i, file) {
if (!/\.(jpe?g|png|gif)$/i.test(file.name)){
return alert(file.name +" is not an image");
} // else...
var reader = new FileReader();
$(reader).on("load", function() {
$preview.append($("<img/>", {src:this.result, height:100}));
});
reader.readAsDataURL(file);
}
}
$('#file-input').on("change", previewImages);<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="file-input" type="file" multiple>
<div id="preview"></div>More info on MDN readAsDataURL
StackOverflow Preview Image, get file size, image height and width before upload
有关MDN readAsDataURL
StackOverflow预览图像的更多信息，上传前获取文件大小、图像高度和宽度
回答by J. Jerez
Just use FileReader.readAsDataURL()
只需使用FileReader.readAsDataURL()
HTML:
HTML：
<div id='photos-preview'></div>
<input type="file" id="fileupload" multiple (change)="handleFileInput($event.target.files)" />
JS:
JS：
function handleFileInput(fileList: FileList) {
const preview = document.getElementById('photos-preview');
Array.from(fileList).forEach((file: File) => {
const reader = new FileReader();
reader.onload = () => {
var image = new Image();
image.src = String(reader.result);
preview.appendChild(image);
}
reader.readAsDataURL(file);
});
}
回答by Shashi Kumar
function previewImages() {
var preview = document.querySelector('#preview');
if (this.files) {
[].forEach.call(this.files, readAndPreview);
}
function readAndPreview(file) {
// Make sure `file.name` matches our extensions criteria
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
return alert(file.name + " is not an image");
} // else...
var reader = new FileReader();
reader.addEventListener("load", function() {
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = this.result;
preview.appendChild(image);
});
reader.readAsDataURL(file);
}
}
document.querySelector('#file-input').addEventListener("change", previewImages);<input id="file-input" type="file" multiple>
<div id="preview"></div>回答by Orgkid
<script type="text/javascript">
var upcontrol = {
queue : null, // upload queue
now : 0, // current file being uploaded
start : function (files) {
// upcontrol.start() : start upload queue
// WILL ONLY START IF NO EXISTING UPLOAD QUEUE
if (upcontrol.queue==null) {
// VISUAL - DISABLE UPLOAD UNTIL DONE
upcontrol.queue = files;
document.getElementById('uploader').classList.add('disabled');
// PREVIEW UPLOAD IMAGES
upcontrol.preview();*enter code here*
//PROCESS UPLOAD ON CLICK
$('#add_files').on('click', function() {
upcontrol.run();
});
}
},
preview : function() {
//upcontrol.preview() : preview uploading file
if (upcontrol.queue) {
var filesAmount = upcontrol.queue.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
var fimg = document.createElement('img')
fimg.src = event.target.result,
fimg.classList = "col-sm-6 col-md-6 col-lg-4 float-left center",
document.getElementById('gallery').appendChild(fimg);
}
reader.readAsDataURL(upcontrol.queue[i]);
}
}
},
run : function () {
// upcontrol.run() : proceed upload file
var xhr = new XMLHttpRequest(),
data = new FormData();
data.append('file-upload', upcontrol.queue[upcontrol.now]);
xhr.open('POST', './lockeroom/func/simple-upload.php', true);
xhr.onload = function (e) {
// SHOW UPLOAD STATUS
var fstat = document.createElement('div'),
txt = upcontrol.queue[upcontrol.now].name + " - ";
if (xhr.readyState === 4) {
if (xhr.status === 200) {
// SERVER RESPONSE
txt += xhr.responseText;
} else {
// ERROR
txt += xhr.statusText;
}
}
fstat.innerHTML = txt;
document.getElementById('upstat').appendChild(fstat);
// UPLOAD NEXT FILE
upcontrol.now++;
if (upcontrol.now < upcontrol.queue.length) {
upcontrol.run();
}
// ALL DONE
else {
upcontrol.now = 0;
upcontrol.queue = null;
document.getElementById('uploader').classList.remove('disabled');
}
};
xhr.send(data);
}
};
window.addEventListener("load", function () {
// IF DRAG-DROP UPLOAD SUPPORTED
if (window.File && window.FileReader && window.FileList && window.Blob) {
/* [THE ELEMENTS] */
var uploader = document.getElementById('uploader');
/* [VISUAL - HIGHLIGHT DROP ZONE ON HOVER] */
uploader.addEventListener("dragenter", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.add('highlight');
});
uploader.addEventListener("dragleave", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.remove('highlight');
});
/* [UPLOAD MECHANICS] */
// STOP THE DEFAULT BROWSER ACTION FROM OPENING THE FILE
uploader.addEventListener("dragover", function (e) {
e.preventDefault();
e.stopPropagation();
});
// ADD OUR OWN UPLOAD ACTION
uploader.addEventListener("drop", function (e) {
e.preventDefault();
e.stopPropagation();
uploader.classList.remove('highlight');
upcontrol.start(e.dataTransfer.files);
});
}
// FALLBACK - HIDE DROP ZONE IF DRAG-DROP UPLOAD NOT SUPPORTED
else {
document.getElementById('uploader').style.display = "none";
}
});
</script>
i used somthing like this and i got the best result and easy to understand.
我使用了这样的东西，我得到了最好的结果并且很容易理解。
回答by Munna ak-17
function appendRows(){
$i++;
var html='';
html+='<div id="remove'+$i+'"><input type="file" name="imagefile[]" accept="image/*" onchange="appendloadFile('+$i+')"><img id="outputshow'+$i+'" height="70px" width="90px"><i onclick="deleteRows('+$i+')" class="fas fa-trash-alt"></i></div>';
$("#appendshow").append(html);
}
function appendloadFile(i){
var appendoutput = document.getElementById('outputshow'+i+'');
appendoutput.src = URL.createObjectURL(event.target.files[0]);
}
回答by J.Doe
$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery"></div>function previewImages() {
var preview = document.querySelector('#preview');
if (this.files) {
[].forEach.call(this.files, readAndPreview);
}
function readAndPreview(file) {
// Make sure `file.name` matches our extensions criteria
if (!/\.(jpe?g|png|gif)$/i.test(file.name)) {
return alert(file.name + " is not an image");
} // else...
var reader = new FileReader();
reader.addEventListener("load", function() {
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = this.result;
preview.appendChild(image);
});
reader.readAsDataURL(file);
}
}
document.querySelector('#file-input').addEventListener("change", previewImages);<input id="file-input" type="file" multiple>
<div id="preview"></div>回答by subham
$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery">$(function() {
// Multiple images preview in browser
var imagesPreview = function(input, placeToInsertImagePreview) {
if (input.files) {
var filesAmount = input.files.length;
for (i = 0; i < filesAmount; i++) {
var reader = new FileReader();
reader.onload = function(event) {
$($.parseHTML('<img>')).attr('src', event.target.result).appendTo(placeToInsertImagePreview);
}
reader.readAsDataURL(input.files[i]);
}
}
};
$('#gallery-photo-add').on('change', function() {
imagesPreview(this, 'div.gallery');
});
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" multiple id="gallery-photo-add">
<div class="gallery">