基于vue。

// 静态数据
const TYPE_LIMIT = {
    img: 'gif/png/jpg/jpeg/bmp',
    file: 'docx/doc/xls/xlsx/pdf',
    all:'gif/png/jpg/jpeg/bmp/docx/doc/xls/xlsx/pdf'
}
var myDownloader = {
    template: `<van-button class="btn confirm-btn" round v-on:click="download">
                {{btnText}}
            </van-button>`,
    props: {
        url: { type: String, required: true},
        filename:{type: String, default: "回执文件"},
        btnText: { type: String, default: "下载"}
    },
    data: () => {
        return {
            isErrorShow: false,
            errorMessage: '异常错误',
            diaContent:''
        }
    },
    mounted(){
        let fileType = this.url.substring(this.url.lastIndexOf(".")+1).toLowerCase()
        this.diaContent = !TYPE_LIMIT.img.split('/').includes(fileType) 
        ? '即将跳转到文件预览，<br>请长按图片下载。'
        : '即将跳转到文件预览，请点击右上角“...”并点击“默认浏览器打开”进行下载。'
    },
    methods: {
        saveFile(){
            location.href = this.url;  // 直接下载
            // load(this.url,this.filename) // 跨域重命名待用
        },
        download() {
            var u = navigator.userAgent
            //,app = navigator.appVersion;
            var isAndroid = u.indexOf('Android') > -1 || u.indexOf('Linux') > -1;
            var isIOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/);
            // 这里调用下载
            function is_weixin() {
                var ua = navigator.userAgent.toLowerCase();
                if (ua.match(/MicroMessenger/i) == "micromessenger") {
                    return true;
                } else {
                    return false;
                }
            }

            var isWeixin = is_weixin();
            if (isWeixin && isIOS) {
                this.$dialog.confirm({
                    title: '温馨提示',
                    message: this.diaContent,
                    confirmButtonText :"确定"
                })
                .then(()=>{
                    this.saveFile()
                })
                .catch();
            } else {
                this.saveFile()
            }       
        }
    }
}