JS判断上传图片格式是否正确

时间：2020-12-10 05:23:15
<!DOCTYPE html>

<html>

<head lang="en">

    <meta charset="UTF-8">

    <title>JS判断上传图片格式是否正确</title>

</head>

<body>

<input type="file" id="file"/>

<input id="btn" type="button" value="button"/>

<script>

    function isPicFile(fileName) {

        //lastIndexOf如果没有搜索到则返回为 -1

        if (fileName.lastIndexOf(".") != -1) {

            var fileType = (fileName.substring(fileName.lastIndexOf(".") + 1, fileName.length)).toLowerCase();

            var suppotFile = new Array();

                suppotFile[0] = "jpg";

                suppotFile[1] = "gif";

                suppotFile[2] = "bmp";

                suppotFile[3] = "png";

                suppotFile[4] = "jpeg";

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

                if (suppotFile[i] == fileType) {

                    return true;

                } else {

                    continue;

                }

            }

            alert("文件类型不合法,只能是jpg、gif、bmp、png、jpeg、png类型！");

            return false;

        } else {

            alert("文件类型不合法,只能是 jpg、gif、bmp、png、jpeg、png类型！");

            return false;

        }

    }

    var oFile = document.getElementById('file');

    var oBtn = document.getElementById('btn');

    oBtn.onclick = function () {

        isPicFile( oFile.value );

    };

</script>

</body>

</html>

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