The content of this article is about the summary (code) of operations on numbers in js. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
1. Get the value of the bit-th bit in the binary form of the number num. Note:
1. Bit starts from 1
2. Returns 0 or 1
3. Example: the binary number of 2 is 10, the first bit is 0, and the second bit is 1
function valueAtBit(num, bit) { var s = num.toString(2); return s[s.length - bit]; } function valueAtBit(num, bit) { //toString转化为二进制,split将二进制转化为数组,reverse()将数组颠倒顺序 var arr = num.toString(2).split("").reverse(); return arr[bit-1]; } function valueAtBit(num, bit) { return (num >> (bit -1)) & 1; }
2. Given a binary string, convert it into the corresponding decimal number
function base10(str) { return parseInt(str,2); }
3. Convert the given number into a binary string. If the string length is less than 8 digits, add 0 to the front to reach 8 digits.
function convertToBinary(num) { //转换为2进制格式 var s = num.toString(2); //获得2进制数长度 var l = s.length; if(l<8){ //声明一个字符串用于补满0 var s1 = "0000000"; var s2 = s1.slice(0,8-l); s = s2+s; } return s; } function convertToBinary(num) { var str = num.toString(2); while(str.length < 8) { str = "0" + str; } return str; } function convertToBinary(num) { var s = num.toString(2); return '00000000'.slice(s.length) + s; } function convertToBinary(num) { return ('00000000' + num.toString(2)).slice(-8); //从倒数第八个开始取}
4. Find the value of multiplying a and b. A and b may be decimals. You need to pay attention to the accuracy of the result.
//根据两个书中精度较高的一个来确定,先将其转换成字符串,然后根据小数点的位置确定小数位数, //字符串长度减去‘.'的位置后还要再减去1得到正确的小数位数,两个取其大,然后用toFixed()函数确定 //结果的小数位数 function multiply(a, b) { //求两个数中精度大的一个 var stra=a.toString(); var strb=b.toString(); var len=Math.max(stra.length-stra.indexOf('.')-1,strb.length-strb.indexOf('.')-1); // return parseFloat(a*b).toFixed(len); }
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