FormData兼容IE10 360及DWR的异步上传原理

摘自：https://github.com/henryluki/FormData/blob/master/formdata.js

if(!window.FormData) {
    (function(self) {
        var BOUNDARY, BlobPart, CRLF, FormData, StringPart, support;
        if (self.FormData) {
            return;
        }
        support = {
            arrayBuffer : !!self.ArrayBuffer,
            blob : !!self.FileReader && !!self.Blob && (function() {
                try {
                    new Blob();
                    return true;
                } catch (_error) {
                    return false;
                }
            })()
        };
        CRLF = "\r\n";
        BOUNDARY = "--------FormData" + Math.random();
        StringPart = (function() {
            function StringPart(name, value) {
                this.name = name;
                this.value = value;
            }

            StringPart.prototype.convertToString = function() {
                var lines;
                lines = [];
                return new Promise((function(_this) {
                    return function(resolve) {
                        lines.push("--" + BOUNDARY + CRLF);
                        lines.push("Content-Disposition: form-data; name=\""
                                + _this.name + "\";" + CRLF + CRLF);
                        lines.push("" + _this.value + CRLF);
                        return resolve(lines.join(''));
                    };
                })(this));
            };

            return StringPart;

        })();
        BlobPart = (function() {
            function BlobPart(name, filename, souce) {
                this.name = name;
                this.filename = filename;
                this.souce = souce;
            }

            BlobPart.prototype._readArrayBufferAsString = function(buff) {
                var view;
                view = new Uint8Array(buff);
                return view.reduce(function(acc, b) {
                    acc.push(String.fromCharCode(b));
                    return acc;
                }, new Array(view.length)).join('');
            };

            BlobPart.prototype._readBlobAsArrayBuffer = function() {
                return new Promise((function(_this) {
                    return function(resolve) {
                        var reader;
                        reader = new FileReader();
                        reader.readAsArrayBuffer(_this.souce);
                        return reader.onload = function() {
                            return resolve(_this
                                    ._readArrayBufferAsString(reader.result));
                        };
                    };
                })(this));
            };

            BlobPart.prototype._readBlobAsBinary = function() {
                return new Promise((function(_this) {
                    return function(resolve) {
                        return resolve(_this.souce.getAsBinary());
                    };
                })(this));
            };

            BlobPart.prototype.convertToString = function() {
                var lines;
                lines = [];
                lines.push("--" + BOUNDARY + CRLF);
                lines.push("Content-Disposition: form-data; name=\"" + this.name
                        + "\"; filename=\"" + this.filename + "\"" + CRLF);
                lines.push("Content-Type: " + this.souce.type + CRLF + CRLF);
                if (support.blob && support.arrayBuffer) {
                    return this._readBlobAsArrayBuffer().then(function(strings) {
                        lines.push(strings + CRLF);
                        return lines.join('');
                    });
                } else {
                    return this._readBlobAsBinary().then(function(strings) {
                        lines.push(strings + CRLF);
                        return lines.join('');
                    });
                }
            };

            return BlobPart;

        })();
        FormData = (function() {
            function FormData() {
                this.polyfill = true;
                this._parts = [];
                this.boundary = BOUNDARY;
            }

            FormData.prototype._stringToTypedArray = function(string) {
                var bytes;
                bytes = Array.prototype.map.call(string, function(s) {
                    return s.charCodeAt(0);
                });
                return new Uint8Array(bytes);
            };

            FormData.prototype.append = function(key, value) {
                var part;
                part = null;
                if (typeof value === "string") {
                    part = new StringPart(key, value);
                } else if (value instanceof Blob) {
                    part = new BlobPart(key, value.name || "blob", value);
                } else {
                    part = new StringPart(key, value);
                }
                if (part) {
                    this._parts.push(part);
                }
                return this;
            };

            FormData.prototype.toString = function() {
                var parts;
                parts = this._parts;
                return Promise.all(this._parts.map(function(part) {
                    return part.convertToString();
                })).then(function(lines) {
                    lines.push("--" + BOUNDARY + "--");
                    return lines.join('');
                }).then(this._stringToTypedArray);
            };

            return FormData;

        })();
        return self.FormData = FormData;
    })(typeof self !== 'undefined' ? self : this);
}

DWR异步上传的核心原理：

// 复制替身
var clone = value.cloneNode(true);
// 移除自身ID
value.removeAttribute("id", prop);
// 设置自身名称
value.setAttribute("name", prop);
// 隐藏自身
value.style.display = "none";
// 插入替身
value.parentNode.insertBefore(clone, value);
// 移除自身
value.parentNode.removeChild(value);
// 加进iframe里的form中
batch.form.appendChild(value);