What is the right way to count all the layers that are going to change into a script?

Question

I am using a script (by Sergey Kritskiy from this question) so to select all shapes with specific color and replace this color with another one. I made some changes, I have also add a confirm window (at step 5) which gives a kind of "report" message before start doing it's stuff. Into the message of confirm window, I have also this layers.length so to inform me how many layers will be change. But every time gives me the same number!!! For example, if I have 300 layers, 150 blue and 150 red, even if I choose to change only blue ones, the layers.length still says 300!!! Here is the script as it looks now...

I remind you that I am new to photoshop scripting and I am not any ace of Java...

function main(){

    var hexToRGB = function(hex) { var r = hex >> 16; var g = hex >> 8 & 0xFF; var b = hex & 0xFF; return [r, g, b]; };

    function SetLayerType() {
        var layerType='';
        while(layerType == null || layerType == ''){
            layerType = prompt('Enter layers type...', '', 'Step 1');
        }                   
        return layerType;
    }
    layerType = SetLayerType();

    function SetLayerName() {
        var layerName = prompt('Enter layers name...', '', 'Step 2');
    }
    layerName = SetLayerName();

    if (confirm('Click "Yes" and choose the color you want to replace...', false, 'Step 3')) {
        if (app.showColorPicker()){
            var color1_decimal = app.foregroundColor.rgb.hexValue;
            var color1_hexadecimal = color1_decimal.toString(16);
            var color1_rgb = hexToRGB(parseInt(color1_hexadecimal, 16));
        };
    }
    else {
        return;
    };

    if (confirm('Click "Yes" and choose the new color...', false, 'Step 4')) {
        if (app.showColorPicker()){
            var color2_decimal = app.foregroundColor.rgb.hexValue;
            var color2_hexadecimal = color2_decimal.toString(16);
            var color2_rgb = hexToRGB(parseInt(color2_hexadecimal, 16));
        };
    }
    else {
        return;
    };

    var layers = getLayersData(),
        sourceColor = [color1_rgb[0], color1_rgb[1], color1_rgb[2]], 
        targetColor = [color2_rgb[0], color2_rgb[1], color2_rgb[2]];
    if (confirm ('You are about to replace color for [' + layers.length + '] shapes in\n[' + activeDocument.name + '] document.\n\nOld color: (' + sourceColor + ')\nNew Color: (' + targetColor + ')\n\nDo you want to continue?',  false, 'Step 5')) {
        var colorToChange = new SolidColor();
        colorToChange.rgb.red = sourceColor[0];
        colorToChange.rgb.green = sourceColor[1];
        colorToChange.rgb.blue = sourceColor[2];
        for (var i = 0; i < layers.length; i++) {
            if (layers[i].color.rgb.hexValue == colorToChange.rgb.hexValue) {
                selectById(layers[i].id);
                changeShapeColor(targetColor);
            }
        }
    }
    else {
        return;
    };

    function getLayersData() {
        var lyrs = [];
        try {
            activeDocument.backgroundLayer;
            var layers = 0
        } 
        catch (e) {
            var layers = 1;
        };
        while (true) {
            ref = new ActionReference();
            ref.putIndex(charIDToTypeID('Lyr '), layers);
            try {
                var desc = executeActionGet(ref);
            } 
            catch (err) {
                break;
            }
            var lyr = {};
            lyr.type = desc.getInteger(stringIDToTypeID("layerKind"));
            lyr.name = desc.getString(charIDToTypeID("Nm  "));
            lyr.id = desc.getInteger(stringIDToTypeID("layerID"));
            if (lyr.type == layerType && lyr.name.match(layerName)) {
                var adj = desc.getList(stringIDToTypeID("adjustment")).getObjectValue(0);
                if (adj.hasKey(stringIDToTypeID("color"))) {
                    var curColor = new SolidColor();
                    curColor.rgb.red = adj.getObjectValue(stringIDToTypeID("color")).getUnitDoubleValue(stringIDToTypeID("red"));
                    curColor.rgb.green = adj.getObjectValue(stringIDToTypeID("color")).getUnitDoubleValue(stringIDToTypeID("grain"));
                    curColor.rgb.blue = adj.getObjectValue(stringIDToTypeID("color")).getUnitDoubleValue(stringIDToTypeID("blue"));
                    lyr.color = curColor;
                    lyrs.push(lyr);
                }
            }
            layers++;            
        }
        return lyrs
    };

    function changeShapeColor(color) {
        var desc8 = new ActionDescriptor();
        var ref1 = new ActionReference();
        ref1.putEnumerated(stringIDToTypeID('contentLayer'), charIDToTypeID('Ordn'), charIDToTypeID('Trgt'));
        desc8.putReference(charIDToTypeID('null'), ref1);
        var desc9 = new ActionDescriptor();
        var desc10 = new ActionDescriptor();
        desc10.putDouble(charIDToTypeID('Rd  '), color[0]);
        desc10.putDouble(charIDToTypeID('Grn '), color[1]);
        desc10.putDouble(charIDToTypeID('Bl  '), color[2]);
        desc9.putObject(charIDToTypeID('Clr '), charIDToTypeID('RGBC'), desc10);
        desc8.putObject(charIDToTypeID('T   '), stringIDToTypeID('solidColorLayer'), desc9);
        executeAction(charIDToTypeID('setd'), desc8, DialogModes.NO);
    };

    function selectById(id) {
        var desc1 = new ActionDescriptor();
        var ref1 = new ActionReference();
        ref1.putIdentifier(charIDToTypeID('Lyr '), id);
        desc1.putReference(charIDToTypeID('null'), ref1);
        executeAction(charIDToTypeID('slct'), desc1, DialogModes.NO);
    };

}
main();

EDIT: If you try the script, at the second step, where asks for layer name, just leave it empty!!!

Answer 1

First of all, your SetLayerName() doesn't return anything and your layerName is undefined. It should be like this:

function SetLayerName() {
    return prompt('Enter layers name...', '', 'Step 2');
}
var layerName = SetLayerName();

Then getLayersData() returns layers that are match for a specific type and name, NOT a specific color. If you want to show how many layers will be changed you should also add this condition before pushing a layer to lyrs: if (curColor.rgb.hexValue == colorToChange.rgb.hexValue) lyrs.push(lyr);

It'd be much easier for you if you'd spend an hour on any JavaScript course on any code teaching platform.

update:

On line 42 and 43 you're defining sourceColor and targetColor from exiting arrays (color1_rgb and color2_rgb) and then on line 54 you're defining colorToChange from sourceColor. Basically you're doing

var color1_rgb = app.foregroundColor.rgb.values; // stripping down the SolidColor object
var layers = getLayersData(); //colorToChange is needed here
var sourceColor = color1_rgb;
var colorToChange = new SolidColor() // uses values of sourceColor;

Both your sourceColor and colorToChange can be defined before getLayersData() because they use values of color1_rgb, that's defined in the beginning. Even more, you're using 3 different variables to define the same thing. You don't need both color1_rgb and sourceColor, you only need to get the color once and then use it for everything.

    var colorToChange = app.foregroundColor;
    var layers = getLayersData();