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[javascript]檔案上傳前，檔案選取的參考範例


HTML 語法：
<input id="FileSelected" type="file" />
   取得檔案

<input id="FileSelected" type="file" multiple="multiple" />
  同時取得多個檔案

<input id="FileSelected" type="file" accept="image/*" />
   限制取得影像檔案




使用 DOM 獲取選擇的檔案：
var selectedFile = document.getElementById('input').files[0];



使用 jQuery 獲取選擇的檔案：
var selectedFile = $('#input').get(0).files[0];
var selectedFile = $('#input')[0].files[0];



使用 change event 獲取選擇的檔案
<input id="input" onchange="handleFiles(this.files)" type="file" />


使用 EventListener 動態地監聽
var inputElement = document.getElementById("inputField");
inputElement.addEventListener("change", handleFiles, false);

function handleFiles() {
  var fileList = this.files;

  /* now you can work with the file list */
}







範例 (Html Page)
<!DOCTYPE html>
<html>
<body onload="myFunction()">

<input type="file" id="myFile" multiple size="50" onchange="myFunction()">

<p id="demo"></p>
    
<script>
function myFunction(){
    var x = document.getElementById("myFile");
    var txt = "";
    if ('files' in x) {
        if (x.files.length == 0) {
            txt = "Select one or more files.";
        } else {
            for (var i = 0; i < x.files.length; i++) {
                txt += "<br><strong>" + (i+1) + ". file</strong><br>";
                var file = x.files[i];
                if ('name' in file) {
                    txt += "name: " + file.name + "<br>";
                }
                if ('size' in file) {
                    txt += "size: " + file.size + " bytes <br>";
                }
            }
        }
    } 
    else {
        if (x.value == "") {
            txt += "Select one or more files.";
        } else {
            txt += "The files property is not supported by your browser!";
            txt  += "<br>The path of the selected file: " + x.value; // If the browser does not support the files property, it will return the path of the selected file instead. 
        }
    }
    document.getElementById("demo").innerHTML = txt;
}
</script>

<p><strong>Tip:</strong> Use the Control or the Shift key to select multiple files.</p>

</body>
</html>



執行結果