This method is used to copy properties of the target object into the source object. In other words, this method merges the source object with the target object and modifies the target object:

    let a = {} 
    Object.assign(a, { age: 25 }) 
    console.log(a)  //{"age":25} 

The first parameter to Object.assign is the target on which source properties are copied. The same target object is returned to the caller. Existing properties are overwritten, while properties that aren't part of the source object are ignored:

    let a = {age : 23, gender: "male"} 
    Object.assign(a, { age: 25 })    // age overwritten, but gender ignored 
    console.log(a)  //{"age":25, "gender":"male"} 

Object.assign can take multiple source objects. You can write Object.assign...