一段JS代码作用

Question

function getBytes(b) {var c, d, e, f, h, i, j, k, l = 0,m = [],g="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";if (b) {    b += "";    do f = g.indexOf(b.charAt(l++)),    h = g.indexOf(b.charAt(l++)),    i = g.indexOf(b.charAt(l++)),    j = g.indexOf(b.charAt(l++)),    k = f << 18 | h << 12 | i << 6 | j,    c = k >> 16 & 255,    d = k >> 8 & 255,    e = 255 & k,    m.push(c),    64 !== i && (m.push(d), 64 !== j && m.push(e));    while (l < b.length)}return m} 一段压缩的js 不知道什么用？转byte好像不是直接转的。