javascript字符串和arrayBuffer转化，responseType：‘arrayBuffer’

字符串–》arrayBuffer

function stringToArrayBuffer(str) { // utf16 不管是字符还是汉字
    let buffer = new ArrayBuffer(str.length * 2);
    let view = new Uint16Array(buffer)
    for (let i = 0; i < str.length; i++) {
        view[i] = str.charCodeAt(i)
    }
    return buffer
}

arrayBuffer–》string

function ArrayBufferToString(buf) {
    return String.fromCharCode(...new Uint16Array(buf))
}

---

function request(url, method = "get") {
    return new Promise((resolve, reject) => {
        let xhr = new XMLHttpRequest();
        xhr.open(method, url, true);
        xhr.responseType = 'arraybuffer';
        xhr.onload = function () {
            resolve(xhr.response);
        }
        xhr.send();
    })
}
request('/download').then(arraybuffer => {
    let b = new Blob([arraybuffer]); 
    let blobUrl = URL.createObjectURL(b);
    let a = document.createElement('a');
    a.href = blobUrl;
    a.download = 'a.pdf';
    document.body.appendChild(a);
    a.click();
    a.remove();
    URL.revokeObjectURL(blobUrl)
})