Javascript parseInt 不将十进制转换为二进制？

parseInt not converting decimal to binary?

提问by Robert Rocha

From my understanding the binary number system uses as set of two numbers, 0's and 1's to perform calculations.

根据我的理解，二进制数系统使用一组两个数字，0 和 1 来执行计算。

Why does:

为什么：

console.log(parseInt("11", 2));return 3and not 00001011? http://www.binaryhexconverter.com/decimal-to-binary-converter

console.log(parseInt("11", 2));返回3而不是00001011？ http://www.binaryhexconverter.com/decimal-to-binary-converter

回答by Walter Chapilliquen - wZVanG

Use toString()instead of parseInt:

使用toString()代替parseInt：

11..toString(2)

var str = "11";
var bin = (+str).toString(2);
console.log(bin)

According JavaScript's Documentation:

根据 JavaScript 的文档：

The following examples all return NaN:

parseInt("546", 2);// Digits are not valid for binary representations

以下示例均返回 NaN：

parseInt("546", 2);//数字对于二进制表示无效

回答by Robo Robok

parseInt(number, base)returns decimalvalue of a number presented by numberparameter in basebase.

parseInt(number, base)返回由base 中的参数表示的数字的十进制值。numberbase

And 11 is binary equivalent of 3 in decimal number system.

11 是十进制数系统中 3 的二进制等价物。

var a = {};

window.addEventListener('input', function(e){
  a[e.target.name] = e.target.value;
  console.clear();
  console.log(  parseInt(a.number, a.base)  );
}, false);

<input name='number' placeholder='number' value='1010'>
<input name='base' placeholder='base' size=3 value='2'>

回答by Jason Cust

As stated in the documentation for parseInt: The parseInt() function parses a string argument and returns an integer of the specified radix(the base in mathematical numeral systems).

如文档parseInt中所述：parseInt() 函数解析字符串参数并返回指定基数（数学数字系统中的基数）的整数。

So, it is doing exactly what it should do: converting a binary value of 11to an integer value of 3.

因此，它正在做它应该做的事情：将 的二进制值转换11为 的整数值3。

If you are trying to convert an integer value of 11to a binary value than you need to use the Number.toStringmethod:

如果您尝试将 的整数值转换11为二进制值，则需要使用以下Number.toString方法：

console.log(11..toString(2)); // 1011

回答by alamnaryab

.toString(2)works when applied to a Numbertype.

.toString(2)应用于Number类型时有效。

255.toString(2)      // syntax error
"255".toString(2);   // 255

var n=255;
n.toString(2);      // 11111111

// or in short
Number(255).toString(2) // 11111111
// or use two dots so that the compiler does
// mistake with the decimal place as in 250.x
255..toString(2)        // 11111111

回答by Melchia

The shortes method I've found for converting a decimal stringinto a binary is:

我发现的用于将十进制字符串转换为二进制的 shortes 方法是：

const input = "54654";
const output = (input*1).toString(2);
print(output);

回答by Simon Wang

The parseInt() function parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).

parseInt() 函数解析字符串参数并返回指定基数（数学数字系统中的基数）的整数。

So you are telling the system you want to convert 11 as binary to an decimal.

所以你告诉系统你想将 11 作为二进制转换为十进制。

Specifically to the website you are referring, if you look closer it is actually using JS to issue a HTTP GET to convert it on web server side. Something like following:

具体到您所指的网站，如果您仔细观察，它实际上是使用 JS 发出 HTTP GET 以在 Web 服务器端进行转换。类似于以下内容：

http://www.binaryhexconverter.com/hesapla.php?fonksiyon=dec2bin&deger=11&pad=false

http://www.binaryhexconverter.com/hesapla.php?fonksiyon=dec2bin°er=11&pad=false

回答by Teocci

This is an old question, however I have another solution that might contribute a little bit. I usually use this function to convert a decimal number into a binary:

这是一个老问题，但是我有另一个可能会有所贡献的解决方案。我通常使用此函数将十进制数转换为二进制数：

function dec2bin(dec) {
    return (dec >>> 0).toString(2);
}

The dec >>> 0converts the number into a byte and then toString(radix)function is called to return a binary string. It is simple and clean.

该dec >>> 0转换成字节，然后数toString(radix)函数被调用返回的二进制字符串。它简单干净。

Note: a radixis used for representing a numeric value. Must be an integer between 2 and 36. For example:

注：aradix用于表示数值。必须是 2 到 36 之间的整数。例如：

• 2 - The number will show as a binary value
• 8 - The number will show as an octal value
• 16 - The number will show as an hexadecimal value

• 2 - 数字将显示为二进制值
• 8 - 数字将显示为八进制值
• 16 - 数字将显示为十六进制值

回答by anshul

I think you should understand the math behind decimal to binary conversion. Here is the simple implementation in javascript.

我认为您应该了解十进制到二进制转换背后的数学原理。这是javascript中的简单实现。

main();

function main() {
    let input  = 12;
    let result = decimalToBinary(input);
    console.log(result);
}

function decimalToBinary(input) {
    let base           = 2;
    let inputNumber    = input;
    let quotient       = 0;
    let remainderArray = [];
    let resultArray    = [];

    if (inputNumber) {
        while (inputNumber) {
            quotient = parseInt(inputNumber / base);

            remainderArray.push(inputNumber % base);

            inputNumber = quotient;
        }
        for (let i = remainderArray.length - 1; i >= 0; i--) {
            resultArray.push(remainderArray[i]); 
        }
        return parseInt(resultArray.join(''));
    } else {
        return `${input} is not a valid input`;
    }
}

回答by jaykay

This worked for me: parseInt(Number, original_base).toString(final_base)

这对我有用： parseInt(Number, original_base).toString(final_base)

Eg: parseInt(32, 10).toString(2) for decimal to binary conversion.

例如： parseInt(32, 10).toString(2) 用于十进制到二进制的转换。

Source: https://www.w3resource.com/javascript-exercises/javascript-math-exercise-3.php

来源：https: //www.w3resource.com/javascript-exercises/javascript-math-exercise-3.php

回答by Isaac

Here is a concise recursive version of a manualdecimal to binary algorithm:

这是手动十进制到二进制算法的简明递归版本：

• Divide decimal number in half and aggregate remainder per operation until value==0 and print concatenated binary string

• Example using 25: 25/2 = 12(r1)/2 = 6(r0)/2 = 3(r0)/2 = 1(r1)/2 = 0(r1) => 10011 => reverse => 11001

  function convertDecToBin(input){
      return Array.from(recursiveImpl(input)).reverse().join(""); //convert string to array to use prototype reverse method as bits read right to left 
  
      function recursiveImpl(quotient){
          const nextQuotient = Math.floor(quotient / 2); //divide subsequent quotient by 2 and take lower limit integer (if fractional)
          const remainder = ""+quotient % 2; //use modulus for remainder and convert to string
          return nextQuotient===0?remainder:remainder + recursiveImpl(nextQuotient); //if next quotient is evaluated to 0 then return the base case remainder else the remainder concatenated to value of next recursive call    
      }
  }
  

• 将十进制数一分为二并聚合每个操作的余数，直到 value==0 并打印连接的二进制字符串

• 使用 25 的示例：25/2 = 12(r1)/2 = 6(r0)/2 = 3(r0)/2 = 1(r1)/2 = 0(r1) => 10011 => 反向 => 11001

  function convertDecToBin(input){
      return Array.from(recursiveImpl(input)).reverse().join(""); //convert string to array to use prototype reverse method as bits read right to left 
  
      function recursiveImpl(quotient){
          const nextQuotient = Math.floor(quotient / 2); //divide subsequent quotient by 2 and take lower limit integer (if fractional)
          const remainder = ""+quotient % 2; //use modulus for remainder and convert to string
          return nextQuotient===0?remainder:remainder + recursiveImpl(nextQuotient); //if next quotient is evaluated to 0 then return the base case remainder else the remainder concatenated to value of next recursive call    
      }
  }