js double bitwise not ~~ All In One

js 双非位运算 ~~

0 vs NaN

const arr = [];
// []
~~arr.pop();
// 0
+arr.pop();
// NaN

const arr = [];
// []
const a = arr.pop();
// undefined
~~a;
// 0
+a;
// NaN

const addStrings = function(str1, str2) {
  let res = '';
  let temp = 0;
  const arr1 = str1.split('');
  const arr2 = str2.split('');
  while (arr1.length || arr2.length || temp) {
    // string => number ✅
    let a = ~~arr1.pop();
    let b = ~~arr2.pop();
    console.log(`a, b`, a, b);
    temp += a + b;
    console.log(`temp`, temp);
    // 字符串相加，要注意先后顺序
    res = (temp % 10) + res;
    // 进位
    temp = temp > 9 ? 1 : 0;
  }
  // 正则表达式去除头部的 0
  return res === "0" ? res : res.replace(/^0+/, '');
}

/*
addStrings([1,0,0,0,0,1].join(``), [4, 5, 6].join(``));
a, b 1 6
temp 7
a, b 0 5
temp 5
a, b 0 4
temp 4
a, b 0 0
temp 0
a, b 0 0
temp 0
a, b 1 0
temp 1
'100457'
*/

const addStrings = function(str1, str2) {
  let res = '';
  let temp = 0;
  const arr1 = str1.split('');
  const arr2 = str2.split('');
  while (arr1.length || arr2.length || temp) {
    // string => number ❌  NaN bug
    let a = +arr1.pop();
    let b = +arr2.pop();
    console.log(`a, b`, a, b);
    temp += a + b;
    console.log(`temp`, temp);
    // 字符串相加，要注意先后顺序
    res = (temp % 10) + res;
    // 进位
    temp = temp > 9 ? 1 : 0;
  }
  // 正则表达式去除头部的 0
  return res === "0" ? res : res.replace(/^0+/, '');
}

addStrings([1,0,0,0,0,1].join(``), [4, 5, 6].join(``));

/*
a, b 1 6
temp 7
a, b 0 5
temp 5
a, b 0 4
temp 4
a, b 0 NaN
temp NaN
a, b 0 NaN
temp NaN
a, b 1 NaN
temp NaN
'NaNNaNNaN457'

*/

demos

const addStrings = function(str1, str2) {
  let res = '';
  let temp = 0;
  const arr1 = str1.split('');
  const arr2 = str2.split('');
  while (arr1.length || arr2.length || temp) {
    // string => number ✅
    // ~~ double bitwise not / 双非位运算
    temp += ~~arr1.pop() + ~~arr2.pop();
    console.log(`temp`, temp);
    // 字符串相加，要注意先后顺序
    res = (temp % 10) + res;
    // 进位
    temp = temp > 9 ? 1 : 0;
  }
  // 正则表达式去除头部的 0
  return res === "0" ? res : res.replace(/^0+/, '');
}

addStrings([1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1].join(``), [4, 5, 6].join(``));

/*
2 x temp 6
temp 4
27 x temp 0
 temp 1
'1000000000000000000000000000466'
*/

❌ NaN bug +0

const addStrings = function(str1, str2) {
  let res = '';
  let temp = 0;
  const arr1 = str1.split('');
  const arr2 = str2.split('');
  while (arr1.length || arr2.length || temp) {
    // string => number ❌  NaN bug
    temp += +arr1.pop() + +arr2.pop();
    console.log(`temp`, temp);
    // 字符串相加，要注意先后顺序
    res = (temp % 10) + res;
    // 进位
    temp = temp > 9 ? 1 : 0;
  }
  // 正则表达式去除头部的 0
  return res === "0" ? res : res.replace(/^0+/, '');
}

addStrings([1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1].join(``), [4, 5, 6].join(``));

/*
temp 7
temp 5
temp 4
28 x temp NaN
'NaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaNNaN457'
*/

!

js 大数相加，科学计数法 bug

const a = parseInt([1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1].join(``));
const b = parseInt([4, 6, 5].join(``));
const sum = a + b;
// 1e+30 ❌

//  wanted ✅
// 1000000000000000000000000000466

(

标签：const,temp,double,NaN,bitwise,js,let,arr1,res
From： https://www.cnblogs.com/xgqfrms/p/17139557.html