JSFiddle - React, Tailwind, and code Playground

HTML

<input type='text' id='name'  />
 <input type='text' id='phone'  />
 <input type='button'  value="save" onclick="saveDataInLS()" />

JavaScript

function saveDataInLS(){
    var obj={};
        obj.name=document.getElementById('name').value;
        obj.phone=document.getElementById('phone').value;
    
    var listObj=localStorage.getItem('DATA');
    if(listObj!=null){
      listObj=JSON.parse(listObj); //this will give array ob object
      listObj.push(obj);
    }else{
      listObj=[obj]; //first time 
    }
   // Save Data in Local Storage 
    localStorage.setItem('DATA',JSON.stringify(listObj)); 
  //Please check Local Storage which will be saved like
    //[{"name":"Anand","phone":"6546456456"}{"name":"Andy","phone":"78688"}]
}