subtrial.ts

function takeFirst<T>(arr: T[]) {
    const firstVal: T = arr[0];
    arr.splice(0, 1);
    return firstVal;
}

SM.addState(State.SubTrial, {
	onEnter: (machine: stateMachine.Machine, blockStruct: BlockStruct) => {
		if (blockStruct.trialArrayURLs.length === 0) {
			// then we need to initialise another trial!
			machine.transition(State.Response, blockStruct);
		} else {
			// then we need to start, or are still, looping through the trial array
			
			// choose the first, or next, image from the trial array
			const thistrial: string = utils.takeFirst(blockStruct.trialArrayURLs);
			
			gorilla.populate('#gorilla', 'subtrial', {thistrial: thistrial});
			$('#gorilla')
				.queue(function () {
					$('.trial-image').show();
					gorilla.refreshLayout();
					$(this).dequeue();
				}) // end queue for '#gorilla'
				.delay(imageDisplayLength)
				.queue(function () {
					// this queue isn't strictly necessary, as we loop through the SubTrial state, replacing the trial image
					$('.trial-image').hide();
					gorilla.refreshLayout();
					$(this).dequeue();
				}) // end queue for '#gorilla'
				.queue(function () {
					// once again, must be inside the queue or it will not display
					machine.transition(State.SubTrial, blockStruct);
					$(this).dequeue();
				}) // end queue for '#gorilla'
		} // end if
	} // end onEnter
}) // end addState State.SubTrial