mortensen - 7 months ago 33

Javascript Question

I want to create an array of all possible combinations of three variables that can either be true or false (i.e. 8 possible combinations).

I am trying to create the cube in the top left corner at this image

So the output should be something like

`points = [`

// first square

{

id: '000',

truths: [false, false, false]

position: [0, 0]

},

{

id: '100',

truths: [true, false, false]

position: [5, 0]

},

{

id: '010',

truths: [false, true, false]

position: [0, 5]

},

{

id: '110',

truths: [true, true, false]

position: [5, 5]

},

// second square

{

id: '001',

truths: [false, false, true]

position: [2.5, 2.5]

},

{

id: '101',

truths: [true, false, true]

position: [7.5, 2.5]

},

{

id: '011',

truths: [false, true, true]

position: [2.5, 7.5]

},

{

id: '111',

truths: [true, true, true]

position: [7.5, 7.5]

},

];

lines = [

{ from: '000', to: '100' },

{ from: '000', to: '010' },

{ from: '000', to: '001' },

{ from: '100', to: '101' },

{ from: '100', to: '110' },

{ from: '001', to: '101' },

{ from: '001', to: '011' },

{ from: '101', to: '001' },

{ from: '101', to: '111' },

...

]

I don't know how to go through all possible truth values and create these points.

One approach could be to use a for loop

`for (var i=0; i<Math.pow(2, 3); i++) {`

...

}

but it doesn't help me assigning the possible truth values.

Answer

Everything in a computer is already binary. You don't need any fancy `Math.pow`

or similar.

```
for (let i = 0; i < 1 << 3; i++) {
console.log([!!(i & (1<<2)), !!(i & (1<<1)), !!(i & 1)]);
}
```

While this looks nice and short, i am actually not a fan of `!!`

or magic numbers. I always fall for these tricks when writing snippets though. Therefore will attempt to give a slightly cleaner version:

```
const AMOUNT_OF_VARIABLES = 3;
for (let i = 0; i < (1 << AMOUNT_OF_VARIABLES); i++) {
let boolArr = [];
//Increasing or decreasing depending on which direction
//you want your array to represent the binary number
for (let j = AMOUNT_OF_VARIABLES - 1; j >= 0; j--) {
boolArr.push(Boolean(i & (1 << j)));
}
console.log(boolArr);
}
```