Javascript 如何从异步函数中获取哈希值?
我使用CryptoJs对PDF文件进行哈希(sha256) 我已经有了我的文件的散列,但我无法在函数外获取它 这是我的代码:Javascript 如何从异步函数中获取哈希值?,javascript,cryptojs,Javascript,Cryptojs,我使用CryptoJs对PDF文件进行哈希(sha256) 我已经有了我的文件的散列,但我无法在函数外获取它 这是我的代码: var reader = new FileReader(); var hash = ""; reader.onloadend = function(evt) { if (evt.target.readyState == FileReader.DONE) { // DONE == 2 var i8a = new Uint8Array(evt.tar
var reader = new FileReader();
var hash = "";
reader.onloadend = function(evt) {
if (evt.target.readyState == FileReader.DONE) { // DONE == 2
var i8a = new Uint8Array(evt.target.result);
var a = []; for (var i = 0; i < i8a.length; i += 4) { a.push(i8a[i] << 24 | i8a[i + 1] << 16 | i8a[i + 2] << 8 | i8a[i + 3]); }
var wordArray = CryptoJS.lib.WordArray.create(a,i8a.length);
var hash = CryptoJS.SHA256(wordArray);
alert(hash);
}
};
var blob = file.slice(0, file.size + 1);
reader.readAsArrayBuffer(blob);
alert(hash);
我的控制台中出现以下错误:
Uncaught TypeError: Cannot read property 'words' of undefined
您需要一个回调函数:
var reader = new FileReader();
var hash = "";
reader.onloadend = function(evt) {
if (evt.target.readyState == FileReader.DONE) { // DONE == 2
var i8a = new Uint8Array(evt.target.result);
var a = []; for (var i = 0; i < i8a.length; i += 4) { a.push(i8a[i] << 24 | i8a[i + 1] << 16 | i8a[i + 2] << 8 | i8a[i + 3]); }
var wordArray = CryptoJS.lib.WordArray.create(a,i8a.length);
var hash = CryptoJS.SHA256(wordArray);
callBack(hash); // <-- callBack at the end of this function
}
};
var blob = file.slice(0, file.size + 1);
reader.readAsArrayBuffer(blob);
function callBack(hash)
{
alert(hash);
}
var reader=newfilereader();
var hash=“”;
reader.onloadend=函数(evt){
如果(evt.target.readyState==FileReader.DONE){//DONE==2
var i8a=新的Uint8Array(evt.target.result);
var a=[];for(var i=0;ivar reader = new FileReader();
var hash = "";
reader.onloadend = function(evt) {
if (evt.target.readyState == FileReader.DONE) { // DONE == 2
var i8a = new Uint8Array(evt.target.result);
var a = []; for (var i = 0; i < i8a.length; i += 4) { a.push(i8a[i] << 24 | i8a[i + 1] << 16 | i8a[i + 2] << 8 | i8a[i + 3]); }
var wordArray = CryptoJS.lib.WordArray.create(a,i8a.length);
var hash = CryptoJS.SHA256(wordArray);
callBack(hash); // <-- callBack at the end of this function
}
};
var blob = file.slice(0, file.size + 1);
reader.readAsArrayBuffer(blob);
function callBack(hash)
{
alert(hash);
}