scripting: create textlayer with mixed styles

How about this?
You can play around with the fontAry.
Important points to note is that AE doesn't really have a method to set Regular, Bold, Italic styles. It's mostly set by a "-", leading to the style. The fontname + style is also very case and space sensitive and some fonts are just harder to get right like Arial.

var proj = app.project;
var itemTotal = proj.numItems;
var projComp = proj.activeItem;
var fontSize = 40;
var margin = 5;

app.beginUndoGroup("CreateText");
var fontAry = ["Impact","MyriadPro-Bold","NuevaStd-Italic","ArialMT"];
for (var fi=0;fi<=fontAry.length-1;fi++){
    var curFont = fontAry[fi];
    var curLay = projComp.layers.addText("text1");
    try{
        curLay.text.sourceText.expression =
        "thisProperty.createStyle().setFontSize(\""+fontSize+"\").setFont(\""+curFont+"\").setText(\""+curFont+"\");";
    }catch(e){}
    if(fi == 0){
        var curLayW = curLay.sourceRectAtTime(0,true).width/2;
        curLay.position.setValue([curLayW,projComp.height/2]);
    }else if(fi > 0){
        var preLayPosX = projComp.layer(curLay.index+1).transform.position.value[0];
        var preLayW = projComp.layer(curLay.index+1).sourceRectAtTime(0,true).width/2;
        var curLayW = curLay.sourceRectAtTime(0,true).width/2;

        curLay.position.setValue([preLayPosX+curLayW+preLayW+margin , projComp.height/2]);
    }
}


app.endUndoGroup();

Existing constructs restrict One Text Layer to One Text Style. As Paul has stated, you'll need to link together multiple Text Layers; to cater to as many Text Styles as you require. HTH

Hi, I'm curious on this. Does inserting expression to the textlayer via scripting works in your situation?

I'm not aware there is even a setStyleAt() expression method, just a getStyleAt() method for grabbing a style from a specific character. I think expressions have the same restrictions of not being able to set multiple styles on a single layer.

So there is no good solution for this sadly. It still comes down to using multiple layers, and at best jumping through hoops working out individual text layer bounds for positioning if you were to try to arrange these different layers. You could also use text animators on multiple duplicate layers to set 0% opacity on one range of characters then the reverse on the other layer, but once you've changed the style there's a high chance the characters across the two layers won't line up.