Change each letter in a text layer to have a random font from set list with a script

Have you thought through the »randomization«? 

With plain »randomness« (and pseudo-randomness) several letters in sequence could assume the same font (similar to rolling dice and getting the same number several times in sequence) and some fonts might be used noticable less than others (or even not at all). 

Maybe this Script can help, the Array »newFonts« containing the fontPostScriptNames; kerning is not considered. (edited)

See the screenshots for an example of what it does: 

Script updated 2022-05-09

// apply font from array to letters of selected type layer;
// 2022, use it at your own risk;
if (app.documents.length > 0) {
//////////////////
try {
var theFonts = new Array;
var theStyleRanges = new Array;
// get font of active layer;
var ref = new ActionReference();
ref.putEnumerated( charIDToTypeID("Lyr "), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") ); 
var layerDesc = executeActionGet(ref);
var layerSet = typeIDToStringID(layerDesc.getEnumerationValue(stringIDToTypeID("layerSection")));
var isBackground = layerDesc.getBoolean(stringIDToTypeID("background"));
var theName = layerDesc.getString(stringIDToTypeID('name'));
// if not layer group collect values;
if (layerSet != "layerSectionEnd" && layerSet != "layerSectionStart" && isBackground != true) {
var hasText = layerDesc.hasKey(stringIDToTypeID("textKey"));
if (hasText == true) {
var textDesc = layerDesc.getObjectValue(stringIDToTypeID('textKey'));
var theText = textDesc.getString(stringIDToTypeID('textKey'));
//var shapeList = textDesc.getList(stringIDToTypeID('textShape'));
var paragraphRangeList = textDesc.getList(stringIDToTypeID('paragraphStyleRange'));
var kernRange = textDesc.getList(stringIDToTypeID('kerningRange'));
var rangeList = textDesc.getList(stringIDToTypeID('textStyleRange'));
// process the list;
for (var o = 0; o < rangeList.count; o++) {
var thisList = rangeList.getObjectValue(o);
var theFrom = thisList.getInteger(stringIDToTypeID('from'));
var theTo = thisList.getInteger(stringIDToTypeID('to'));
var styleDesc = thisList.getObjectValue(stringIDToTypeID('textStyle'));
var aSize = styleDesc.getUnitDoubleValue(charIDToTypeID( "Sz  " ));
// check for default font;
if (styleDesc.hasKey(stringIDToTypeID('fontPostScriptName')) == true) {var aFont = styleDesc.getString(stringIDToTypeID('fontPostScriptName'))}
else {
	var theDefault = styleDesc.getObjectValue(stringIDToTypeID('baseParentStyle'));	
	var aFont = theDefault.getString(stringIDToTypeID('fontPostScriptName'));
	};
if (styleDesc.hasKey(stringIDToTypeID('impliedFontSize')) == true) {var aFont = styleDesc.getString(stringIDToTypeID('fontPostScriptName'))}
// add to array;
//////////////////
if (o == 0) {
    theFonts.push([aFont, aSize, theFrom, theTo]);
    theStyleRanges.push(thisList.getObjectValue(stringIDToTypeID('textStyle')));
    };
if (o > 0 && theFrom != theFonts[theFonts.length - 1][2] /*&& theTo != theFonts[theFonts.length - 1][3]*/) {
theFonts.push([aFont, aSize, theFrom, theTo]);
theStyleRanges.push(thisList.getObjectValue(stringIDToTypeID('textStyle')));
};
//////////////////
}
}
};
//alert (theFonts.length+"\n"+theFonts.join("\n"));
// the replacement-fonts array;
var newFonts = ["MyriadPro-Regular", "MyriadPro-Bold", "Times-BoldItalic"];
var anIndex = 0;
var theFontsNumber = newFonts.length;
// change text;
// =======================================================
var idPxl = charIDToTypeID( "#Pxl" );
var idTxtt = charIDToTypeID( "Txtt" );
var idFrom = charIDToTypeID( "From" );
var idT = charIDToTypeID( "T   " );
var idTxtS = charIDToTypeID( "TxtS" );
var idTxLr = charIDToTypeID( "TxLr" );
var idTxt = charIDToTypeID( "Txt " );
var idsetd = charIDToTypeID( "setd" );
    var desc6 = new ActionDescriptor();
    var idnull = charIDToTypeID( "null" );
        var ref1 = new ActionReference();
        ref1.putEnumerated( idTxLr, charIDToTypeID( "Ordn" ), charIDToTypeID( "Trgt"  ));
    desc6.putReference( idnull, ref1 );
        var desc7 = new ActionDescriptor();
        desc7.putString( idTxt, theText );
            var list2 = new ActionList();
//////////////////
// define each letter individually;
var theIndex = 0;
var thisStyleRange = theStyleRanges[theIndex];
var thisFont = theFonts[theIndex];
for (var m = 0; m < theText.length; m++) {
// check for relevant style range;
    if (m == thisFont[3]) {
        theIndex++;
        var thisStyleRange = theStyleRanges[theIndex];
        var thisFont = theFonts[theIndex];
        };
// apply style range but change font;
    var desc14 = new ActionDescriptor();
    desc14.putInteger( idFrom, m );
    desc14.putInteger( idT, m+1 );
        var desc15 = new ActionDescriptor();
        var desc15 = thisStyleRange;
        var aRandomFont = newFonts[Math.floor(Math.random()*3)];
        desc15.putString( stringIDToTypeID( "fontPostScriptName" ), aRandomFont);
    desc14.putObject( idTxtS, idTxtS, desc15 );
    list2.putObject( idTxtt, desc14 );
    };
//////////////////
var desc7 = new ActionDescriptor();
var list3 = new ActionList();
    for (var n = kernRange.count-1; n >= 0; n--) {
        var thisOne = kernRange.getObjectValue(n);
        var desc15 = new ActionDescriptor();
        desc15.putInteger( idFrom, thisOne.getInteger(charIDToTypeID("From")) );
        desc15.putInteger( idT, thisOne.getInteger(charIDToTypeID( "T   " )) );
        desc15.putInteger( charIDToTypeID( "Krng" ), thisOne.getInteger(stringIDToTypeID("kerning")));
        list3.putObject( stringIDToTypeID( "kerningRange"),  desc15);
        };
        desc7.putList( idTxtt, list2 );
        desc7.putList( stringIDToTypeID( "kerningRange"), list3);
    desc6.putObject( idT, idTxLr, desc7 );
executeAction( idsetd, desc6, DialogModes.NO );
}
catch (e) {};
};
//////////////////

You have to use Action Manager code to style text within a TextItem.

I have a sample script that you can modify, this splits a TextItem into lines and applies formatting but you can loop it with each character if you wanted.

----------------------------------

/*
Utility PS Scripts created by David M. Converse ©2018-21

This script replaces text and sets styling

Last modified 6/2/2021

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#target photoshop

layerUpdate();

function setFormatting(start, end, fontName, fontStyle, fontSize){ //format text per input
    var idsetd = app.charIDToTypeID('setd');
    var action = new ActionDescriptor();
    var idnull = app.charIDToTypeID('null');
    var reference = new ActionReference();
    var idTxLr = app.charIDToTypeID('TxLr');
    var idOrdn = app.charIDToTypeID('Ordn');
    var idTrgt = app.charIDToTypeID('Trgt');
    reference.putEnumerated(idTxLr, idOrdn, idTrgt);
    action.putReference(idnull, reference);
    var idT = app.charIDToTypeID('T   ');
    var textAction = new ActionDescriptor();
    var idTxtt = app.charIDToTypeID('Txtt');
    var actionList = new ActionList();
    var textRange = new ActionDescriptor();
    var idFrom = app.charIDToTypeID('From');
    textRange.putInteger(idFrom, start);
    textRange.putInteger(idT, end);
    var idTxtS = app.charIDToTypeID('TxtS');
    var formatting = new ActionDescriptor();
    var idFntN = app.charIDToTypeID('FntN');
    formatting.putString(idFntN, fontName);
    var idFntS = app.charIDToTypeID('FntS');
    formatting.putString(idFntS, fontStyle);
    var idSz = app.charIDToTypeID('Sz  ');
    var idPnt = app.charIDToTypeID('#Pnt');
    formatting.putUnitDouble(idSz, idPnt, fontSize);
    textRange.putObject(idTxtS, idTxtS, formatting);
    actionList.putObject(idTxtt, textRange);
    textAction.putList(idTxtt, actionList);
    action.putObject(idT, idTxLr, textAction);
    app.executeAction(idsetd, action, DialogModes.NO);
	}

function layerUpdate(){
    //sample values
        var size1 = 96
        var size2 = 42;
        var font1 = 'Calibri';
        var style1 = 'bold';
        var texth = 220;
        var textw = 460;
    
    if(documents.length > 0){
        var originalDialogMode = app.displayDialogs;
        app.displayDialogs = DialogModes.ERROR;
        var originalRulerUnits = preferences.rulerUnits;
        var j = 0;
        try{
            var docRef = activeDocument;
            preferences.rulerUnits = Units.POINTS;
            var m = 0;
            for(var i = 0; i < docRef.artLayers.length; i++){
                var LayerRef = docRef.artLayers[i];
                if(LayerRef.kind == LayerKind.TEXT){
                    var TextRef = LayerRef.textItem;
                    TextRef.textComposer = TextComposer.ADOBESINGLELINE;
                    var layerText = TextRef.contents;
                    //can iterate through multiple find/replace pairs
                    var newText = layerText.replace('old', 'new');
                    newText = newText.replace('old-1', 'new-1');
                    newText = newText.replace('old-2', 'new-2');
                    if(newText != layerText){
                        j = i;
                        TextRef.contents = newText;
                        if(TextRef.size == size1){
                            TextRef.size = size2;
                            TextRef.font = font1;
                            TextRef.useAutoLeading = false;
                            TextRef.leading = size2;
                            var l = TextRef.contents.split(/\r/);
                            docRef.activeLayer = LayerRef;
                            setFormatting(0, l[0].length, font1, style1, size1); //send to formatting function
                            preferences.rulerUnits = Units.PIXELS;
                            if(TextRef.kind == TextType.PARAGRAPHTEXT){
                                TextRef.height = texth;
                                TextRef.width = textw;
                                }
                            preferences.rulerUnits = Units.POINTS;
                            break;
                            }
                        }
                    }
                }
            }
        catch(e){
            alert(e + '  ' + e.line);
            preferences.rulerUnits = originalRulerUnits;
            app.displayDialogs = originalDialogMode;
            return;
            }
        preferences.rulerUnits = originalRulerUnits;
        app.displayDialogs = originalDialogMode;
        }
    else{
        alert('You must have a document open to run this script.');
        return;
        }
    }

How complex are the Type Layers? 

Do they combine different colors, font sizes, leading, tracking, kerning, …?