Salesforce4U

 LWC engine can track changes or value assigned to a field or primitive properties automatically, however if field/properties is array or object type then LWC will not be able track value change automatically.  That is when @track is helpful, this will tell LWC engine to observe changes to the properties of object or elements of array decorated with @track. Here is my component code We  can also achieve using spread operator, the key here is instead of mutating same object/array we can create copy and make changes. LWC framework observes value assigned to field/property and if new value !=== previous value then component re-renders. this.address = {...this.address,"city":event.target.value} < template >     < lightning-card title = "2 way Data Binding" >         < div class = "slds-m-around_medium" >             < lightning-input type = "text" label = "Enter course Name"     ...