vue modify the array, dom has not updated question

vue, we will frequently operate a variety of data, but sometimes found after you modify data, dom not updated?

For example, there is an array of objects:

obj = [{'name': 'joy'},{'name': 'bowen'}]

I want to insert a property through the bad, or modify the value of a property:

for (the let I = 0; I <obj.length; I ++) {
　　obj [I] .year = '20 is'
}
found successful array can be modified, but does not update the dom element, that is why?

The reason: change vue intercepted object, but can not monitor the objects change their properties, so I can not update dom, unless we update this array:

this.$set( target , key , value )

Forced to render the page

target: To change the data sources (which may be an object or array);

key: specific data to be changed;

value: re-assigned value;

 

Hope this helps!