it should definitely be telling you when you're missing a semicolon

elements.customcool = {
    color: ["#0000FF", "#FFFFFF", "#0000FF"],
    onSelect: function() {
        var answer4 = parseInt(prompt("Please input the desired temperature decrease per tick. (In celsius)",(cc|undefined)));
        if (!answer4) { return }
        ct = answer4;
        if (isNaN(answer4)) {
            ct = 100
        }
    },
    tool: function(pixel) {
        pixel.temp = pixel.temp - ct,
        pixelTempCheck(pixel)
    },
    category: "tools",
};

elements.customcool = {
    color: ["#0000FF", "#FFFFFF", "#0000FF"],
    onSelect: function() {
        var answer4 = parseInt(prompt("Please input the desired temperature decrease per tick. (In celsius)",(cc|undefined)));
        if (!answer4) { return }
        ct = answer4;
        if (isNaN(answer4)) {
            ct = 100
        }
    },
    tool: function(pixel) {
        pixel.temp = pixel.temp - ct,
        pixelTempCheck(pixel)
    },
    category: "tools",
};

elements.customcool = {
    color: ["#0000FF", "#FFFFFF", "#0000FF"],
    onSelect: function() {
        var answer4 = parseInt(prompt("Please input the desired temperature decrease per tick. (In celsius)",(cc|undefined)));
        if (!answer4) { return }
        ct = answer4;
        if (isNaN(answer4)) {
            ct = 100
        }
    },
    tool: function(pixel) {
        pixel.temp = pixel.temp - ct,
        pixelTempCheck(pixel)
    },
    category: "tools",
};

elements.customcool = {
    color: ["#0000FF", "#FFFFFF", "#0000FF"],
    onSelect: function() {
        var answer4 = parseInt(prompt("Please input the desired temperature decrease per tick. (In celsius)",(cc|undefined)));
        if (!answer4) { return }
        ct = answer4;
        if (isNaN(answer4)) {
            ct = 100
        }
    },
    tool: function(pixel) {
        pixel.temp = pixel.temp - ct,
        pixelTempCheck(pixel)
    },
    category: "tools",
};