Find only tofu square in Indesign using Indesign Extendscript

I tried with 

var doc = app.activeDocument;

// --- Create / get highlight color ---
var highlightColor;
var existingColor = doc.colors.itemByName("JunkHighlight");

if (existingColor.isValid) {
    highlightColor = existingColor;
} else {
    highlightColor = doc.colors.add({
        name: "JunkHighlight",
        model: ColorModel.PROCESS,
        space: ColorSpace.RGB,
        colorValue: [255, 0, 0]
    });
}

// --- Create / get character style ---
var highlightStyle;
var existingStyle = doc.characterStyles.itemByName("JunkCharStyle");

if (existingStyle.isValid) {
    highlightStyle = existingStyle;
} else {
    highlightStyle = doc.characterStyles.add({
        name: "JunkCharStyle",
        fillColor: highlightColor
    });
}

// --- Loop through all stories and characters ---
var stories = doc.stories;
for (var s = 0; s < stories.length; s++) {
    var chars = stories[s].characters;
    for (var i = 0; i < chars.length; i++) {
        var c = chars[i].contents;
        if (typeof c === "string" && c.length > 0 && c.charCodeAt(0) > 127) {
            chars[i].appliedCharacterStyle = highlightStyle;
        }
    }
} this code it provides the output like 

look here it find all the junk but i only need to find the tofu square box.