js 进制转换：十六进制转十进制、十进制转十六进制、十六进制转ASCII码、

因为近期做小程序，蓝牙连接硬件，需要根据module bus通信协议解析数据，用到了很多标题的算法转换，借此总结一下。

十六进制 转 十进制

function hex2dec(hex) {
  var len = hex.length,
    a = new Array(len),
    code;
  for (var i = 0; i < len; i++) {
    code = hex.charCodeAt(i);
    if (48 <= code && code < 58) {
      code -= 48;
    } else {
      code = (code & 0xdf) - 65 + 10;
    }
    a[i] = code;
  }
  return a.reduce(function (acc, c) {
    acc = 16 * acc + c;
    return acc;
  }, 0);
}

十进制 转 十六进制

function dec2hex(val) {
  return ("0" + (Number(val).toString(16))).toUpperCase()

  //return ("0" + (Number(val).toString(16))).slice(-2).toUpperCase()
}

十六进制 转 二进制 （需要借用到hex2dec，也就是需要先转换成十进制，再转换成二进制）

function hex2bin(hex, len) {
  var res = hex_dec(hex).toString(2);
  return (Array(len).join(0) + res).slice(-len);
}

二进制 转 十六进制（网上的一种办法）

function bin2hex(str) {
  let hex_array = [{ key: 0, val: "0000" }, { key: 1, val: "0001" }, { key: 2, val: "0010" }, { key: 3, val: "0011" }, { key: 4, val: "0100" }, { key: 5, val: "0101" }, { key: 6, val: "0110" }, { key: 7, val: "0111" },
    { key: 8, val: "1000" }, { key: 9, val: "1001" }, { key: 'a', val: "1010" }, { key: 'b', val: "1011" }, { key: 'c', val: "1100" }, { key: 'd', val: "1101" }, { key: 'e', val: "1110" }, { key: 'f', val: "1111" }]
  let value = ''
  let list = []
  if (str.length % 4 !== 0) {
    let a = "0000"
    let b = a.substring(0, 4 - str.length % 4)
    str = b.concat(str)
  }
  while (str.length > 4) {
    list.push(str.substring(0, 4))
    str = str.substring(4);
  }
  list.push(str)
  for (let i = 0; i < list.length; i++) {
    for (let j = 0; j < hex_array.length; j++) {
      if (list[i] == hex_array[j].val) {
        value = value.concat(hex_array[j].key)
        break
      }
    }
  }
  return value
}

十六进制 转 ArrayBuffer

function hex2buf(hexStr) {
  var count = hexStr.length / 2;
  let buffer = new ArrayBuffer(count);
  let dataView = new DataView(buffer);
  for (var i = 0; i < count; i++) {
    var curCharCode = parseInt(hexStr.substr(i * 2, 2), 16);
    dataView.setUint8(i, curCharCode);
  }
  return buffer;
}

参考链接1

参考链接2

参考链接3

ArrayBuffer 转 十六进制

function buf2hex(buffer) { // buffer is an ArrayBuffer
  return Array.prototype.map.call(new Uint8Array(buffer), x => ('00' + x.toString(16)).slice(-2)).join('');
}

十六进制 转 ASCII码

function hex2ascll(hexCharCodeStr) {
  var trimedStr = hexCharCodeStr.trim();
  var rawStr = trimedStr.substr(0, 2).toLowerCase() === "0x" ? trimedStr.substr(2) : trimedStr;
  var len = rawStr.length;
  if (len % 2 !== 0) {
    alert("存在非法字符!");
    return "";
  }
  var curCharCode;
  var resultStr = [];
  for (var i = 0; i < len; i = i + 2) {
    curCharCode = parseInt(rawStr.substr(i, 2), 16);
    resultStr.push(String.fromCharCode(curCharCode));
  }
  return resultStr.join("");
}

字符串 转 byte

 function string2byte(str) {
  var ch, st, re = [];
  for (var i = 0; i < str.length; i++) {
    ch = str.charCodeAt(i);  // get char
    st = [];                 // set up "stack"
    do {
      st.push(ch & 0xFF);  // push byte to stack
      ch = ch >> 8;          // shift value down by 1 byte
    }
    while (ch);
    // add stack contents to result
    // done because chars have "wrong" endianness
    re = re.concat(st.reverse());
  }
  // return an array of bytes
  return re;
}