如何在页面加载时读取Xlsx文件并在JavaScript中解析为JSON？

Question

我正在使用http://sheetjs.com中的工作表js库。 我正在尝试在onload期间加载excel文件并将其解析为JSON，但我可以看到只有在均匀更改（例如，更改，文件上传，单击）期间读取文件的选项。有使用node js的选项，但我想使用javascript探索。 在javascript加载期间准备excel文件的可能方法是什么？

JavaScript代码

var X = XLSX;
var XW = {
msg: 'xlsx',
worker: './xlsxworker.js'
};

var global_wb;

var process_wb = (function() {
var OUT = document.getElementById('out');
var HTMLOUT = document.getElementById('htmlout');

var get_format = (function() {
    var radios = document.getElementsByName( "format" );
    return function() {
        for(var i = 0; i < radios.length; ++i) if(radios[i].checked || 
  radios.length === 1) return 'json';
    };
})();

var to_json = function to_json(workbook) {
    var result = {};
    workbook.SheetNames.forEach(function(sheetName) {
        var roa = X.utils.sheet_to_json(workbook.Sheets[sheetName], 
 {header:1});
        if(roa.length) result[sheetName] = roa;
    });
    return JSON.stringify(result, 2, 2);
};
return function process_wb(wb) {
    global_wb = wb;
    var output = "";
    output = to_json(wb);
    if(OUT.innerText === undefined) OUT.textContent = output;
    else OUT.innerText = output;
    if(typeof console !== 'undefined') console.log("output", new Date());
};
})();

var setfmt = window.setfmt = function setfmt() { if(global_wb) 
process_wb(global_wb); };

var b64it = window.b64it = (function() {
var tarea = document.getElementById('b64data');
console.log(tarea);
return function b64it() {
    if(typeof console !== 'undefined') console.log("onload", new Date());

    var wb = X.read(tarea.value, {type:'base64', WTF:false});
    process_wb(wb);
};
 })();

var do_file = (function() {
var rABS = typeof FileReader !== "undefined" && (FileReader.prototype||
{}).readAsBinaryString;
var domrabs = document.getElementsByName("userabs")[0];
if(!rABS) domrabs.disabled = !(domrabs.checked = false);

var use_worker = typeof Worker !== 'undefined';
var domwork = document.getElementsByName("useworker")[0];
if(!use_worker) domwork.disabled = !(domwork.checked = false);

var xw = function xw(data, cb) {
    var worker = new Worker(XW.worker);
    worker.onmessage = function(e) {
        switch(e.data.t) {
            case 'ready': break;
            case 'e': console.error(e.data.d); break;
            case XW.msg: cb(JSON.parse(e.data.d)); break;
        }
    };
    worker.postMessage({d:data,b:rABS?'binary':'array'});
};

return function do_file(files) {
    rABS = domrabs.checked;
    use_worker = domwork.checked;
    var f = files[0];
    console.log(files);
    var reader = new FileReader();

    reader.onload = function(e) {
        if(typeof console !== 'undefined') console.log("onload", new Date(), rABS, use_worker);
        var data = e.target.result;
        if(!rABS) data = new Uint8Array(data);
        if(use_worker) xw(data, process_wb);
        else process_wb(X.read(data, {type: rABS ? 'binary' : 'array'}));
    };
    if(rABS) reader.readAsBinaryString(f);
    else reader.readAsArrayBuffer(f);
};
})();

(function() {
var drop = document.getElementById('drop');
if(!drop.addEventListener) return;

function handleDrop(e) {
    e.stopPropagation();
    e.preventDefault();
    do_file(e.dataTransfer.files);
}

function handleDragover(e) {
    e.stopPropagation();
    e.preventDefault();
    e.dataTransfer.dropEffect = 'copy';
}

drop.addEventListener('dragenter', handleDragover, false);
drop.addEventListener('dragover', handleDragover, false);
drop.addEventListener('drop', handleDrop, false);
})();

(function() {
var xlf = document.getElementById('xlf');
if(!xlf.addEventListener) return;
function handleFile(e) {
do_file(e.target.files); }
xlf.addEventListener('change', handleFile, false);
})();