I installed the three.js plugin for blender to export models to json format, i test it with very simple model contains materials of colors without textures but i get errors if i choose materials in options as in attached image, when i do not choose materials option i can export it but get error in reading it with JSONLoader, the error is "can not read property length of undefined" in three.min.js:264
the blender errors the exported json file
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You haven't added your code here but I think your problem is that when you don't export the material from blender, you have to make your own material; then assign it in JSON loader. If you try to get the material from the JSON file it obviously is nonexistent.
I have faced this error many times. Mainly because I wasn't using the latest releases of three.js or the exporter. If you are using a tutorial check that too.