day3.js

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var slopeRows = input.split("\n");

// part 1
var numTrees = slopeRows.map((line,index) => {
    return line.charAt((index * 3) % line.length) === "#" ? 1 : 0;
}).reduce((acc, val) => acc + val);
console.log(numTrees);

// part 2
var productOfNumTrees = [
    { right:1, down:1 },
    { right:3, down:1 },
    { right:5, down:1 },
    { right:7, down:1 },
    { right:1, down:2 },
].map( direction =>  {
    var numTrees = slopeRows.map((foo,index) => {
        var i = index * direction.down;
        var line = slopeRows[i];
        return (i <= slopeRows.length) && line.charAt((index * direction.right) % line.length) === "#" ? 1 : 0;
    }).reduce((acc, val) => acc + val);
    return numTrees;
}).reduce((acc, val) => acc * val, 1);
console.log(productOfNumTrees);