Discussion on: Daily Challenge #142 - Parts of a Whole

const input = 999999

const output = []

Array.prototype.hasPair = function([a, b])
{
    return this.findIndex(([_a, _b]) => (a === _a && b === _b) || (a === _b && b === _a)) > -1
}

const inputString = input + ''
for(let i = 0; i < inputString.length; i++)
{
    for(let j = i + 1; j < inputString.length; j++)
    {
        const pair = [+inputString[i], +inputString[j]]

        if(!output.hasPair(pair))
        {
            output.push(pair)
        }
    }
}

const outputSum = output.map(([a, b]) => a + b)

console.log(outputSum)