0.1 + 0.2
//0.30000000000000004
0.1 + 0.2 在什麼情況下不等于0.3?
0.1 轉換成二進制 0.0001100110011001100110011001100110011001100110011001101
0.2 轉換成二進制 0.001100110011001100110011001100110011001100110011001101
0.1+0.2 = 0.0001100110011001100110011001100110011001100110011001101 + 0.0011001100110011001100110011001100110011001100110011010 = 0.010011001100110011001100110011001100110011001100...(0.30000000000000004)
JavaScript内部所有的數字都是以64位浮點數形式儲存的,第一位,符号位,0表示正數,1表示負數;第2-11位:指數部分;第13-64位小數部分,當超過52位時,會被截斷,這樣精度就會丢失
解決辦法:
把數字轉化為整數
function add(num1,num2){
let max = 0;
Object.keys(arguments).forEach(arg => {
let decimalLen = arguments[arg].toString().split('.')[1].length
decimalLen > max ? max = decimalLen : null;
})
let p = Math.pow(10,max)
console.log(p);
return (num1 * p + num2 * p)/p
}
3.008 + 3.02 // 6.0280000000000005
add(3.008,3.02) // 6.028
0.1 + 0.2 // 0.30000000000000004
add(0.1,0.2) // 0.3