mortensen - 1 year ago 103
Javascript Question

Generating all possible true/false combinations

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.

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);
}``````

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