Find last matching object in array of objects

var previousInShapeType, index = fruits.length - 1;
for ( ; index >= 0; index--) {
    if (fruits[index].shape == currentShape) {
        previousInShapeType = fruits[index];
        break;
    }
}

You can also loop backwards through array.

Fiddle: http://jsfiddle.net/vonn9xhm/

You can transform your array to an array boolean type and get the last true index.

const lastIndex = fruits.map(fruit => 
  fruit.shape === currentShape).lastIndexOf(true);

var fruit = fruits.slice().reverse().find(fruit => fruit.shape === currentShape);