If you have an expression with more than one line and want to apply it with a Jsx script, You have convert it like this:
// An After Effects expression:
var wiggleAmount = effect("Wiggle Amount")("Slider");
wiggle( 4, wiggleAmount );
// Converted expression for a jsx script:
'var wiggleAmount = effect("Wiggle Amount")("Slider");' + '\n' +
'wiggle( 4, wiggleAmount );'
Put your expressions in "exp.txt" and run the script. Your expressions in the txt file will be converted.