当只有一个为真时，for循环中的所有三个if语句都会触发（JavaScript）

Question

This has me a little stumped. Whenever I execute this code, if one of the if statements in the for loop are true, all three sub-arrays of weaknessArray get effected. The same thing happens when each if statement is in it's own for loop and if instead of one 2D array I use a three separate arrays, one for each for loop.

var typeChart = [2,2,2,2,2,2,4,2,2,2,2,2,2,0,2,2,2,2];
var blankArray = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
var weaknessArray = [blankArray,blankArray,blankArray];

for(i = 0; i<18; i++){
if(typeChart[i] === 0) weaknessArray[2][i] = 1;
if(typeChart[i] === 1) weaknessArray[1][i] = 1;
if(typeChart[i] === 4) weaknessArray[0][i] = 1;

console.log(weaknessArray);
}

Answer 1

There is only ever one blankArray object in memory; your weaknessArray contains three references to the same object .

Create copies instead with .slice , so that you have three arrays (well, four, counting the original) in memory instead of one:

 var typeChart = [2,2,2,2,2,2,4,2,2,2,2,2,2,0,2,2,2,2]; var blankArray = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]; var weaknessArray = [blankArray.slice(), blankArray.slice(), blankArray.slice()]; for(i = 0; i<18; i++){ if(typeChart[i] === 0) weaknessArray[2][i] = 1; if(typeChart[i] === 1) weaknessArray[1][i] = 1; if(typeChart[i] === 4) weaknessArray[0][i] = 1; console.log(weaknessArray); }