Adobe Illustrator: loading a file example

loadFile.jsx

// refer to "JavaScript Tools Guide" for more information about File object.
// https://www.adobe.com/content/dam/acom/en/devnet/scripting/estk/javascript_tools_guide.pdf

function loadFile(){
    var data;
    try{
       var f = File.openDialog("select input file");
        if(f == null) return;
        
        if(!f.open("r")){
            alert("failed to load");
            return null;
        }
        
        data = f.read();
        f.close();
    } catch(e){
        alert("failed to load:" + e.message);
        return null;
    }
    var lines = data.split("\n");

    alert(lines[0]);
    return lines;
}

var lines = loadFile();