摘录自exploringjs

const BIG_ENDIAN = Symbol('BIG_ENDIAN');
const LITTLE_ENDIAN = Symbol('LITTLE_ENDIAN');
function getPlatformEndianness() {
    const arr32 = Uint32Array.of(0x12345678);
    const arr8 = new Uint8Array(arr32.buffer);
    switch ((arr8[0]*0x1000000) + (arr8[1]*0x10000) + (arr8[2]*0x100) + (arr8\
[3])) {
        case 0x12345678:
            return BIG_ENDIAN;
        case 0x78563412:
            return LITTLE_ENDIAN;
        default:
            throw new Error('Unknown endianness');
    }
}

node.js的os模块也有endianness方法