Interview string completion

Time:2021-5-11

demand

Converts the given number to a binary string. If the length of the string is less than 8 bits, 0 will be filled to the full 8 bits.

Examples

input

65

output

01000001

solution

Mode 1 uses the cycle to fill the left zero

function convertToBinary(num) {
    var str = num.toString(2);
    while(str.length < 8) {
        str = "0" + str;
    }
    return str;
}

Mode 2 fixed length zero compensation slice

function convertToBinary(num) {
  return ('00000000' + num.toString(2)).slice(-8);
}

Mode 3: calculate first and then fill in

function convertToBinary(num) {
    var str = num.toString(2);
    return "0".repeat(8 - str.length) + str;
}

For es8 +, mode 4 can be done in one line

function convertToBinary(num) {
    return num.toString(2).padStart(8,"0")
}

Summary

Mode 1 costs a little bit more memory than mode 2, because it keeps generating new variables.
The last one needs high version JS support, which is simple and direct.

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