Add an object at first place in an array

JsHelper.js

var list = data; // here data is itself an array
list.splice(0, 0, 
            {
              definition_id: "-1", // key value pair
              display_name: ""
             }
           );

function replaceAt(string, index, replace) {
        return string.substring(0, index) + replace + string.substring(index + 1);
    }


function sayHello() {
   document.write("Hello, Coding Ground!");
   
    var time_1 = performance.now();
   var arr = [23, 45, 12, 67];
arr = [34, ...arr]; // RESULT : [34,23, 45, 12, 67]

document.write(arr);
 var time_2 = performance.now();
 document.write("HELLO");
 document.write("\n\n"+(time_2-time_1)+"\n\n\n");
 var case1 = (time_2-time_1);
 document.write("HELLO");
 
 
 var time_3 = performance.now();
  var arr = [23, 45, 12, 67];
arr.unshift(34);

document.write(arr);
 var time_4 = performance.now();
 document.write("HELLO");
 document.write("\n\n"+(time_4-time_3)+"\n\n\n");
 var case2 = (time_4-time_3);
 document.write("HELLO");
 
 
 var time_5 = performance.now();
   var arr = [23, 45, 12, 67];
arr.splice(0, 0, 
            {
              definition_id: "-1", // key value pair
              display_name: ""
             }
           );

document.write(arr);
 var time_6 = performance.now();
 document.write("HELLO");
 document.write("\n\n"+(time_6-time_5)+"\n\n\n");
 var case3 = (time_6-time_5);
 document.write("HELLO");
 
 document.write ("<br>");
 
 var mul = 1;
 
 document.write (case1*mul);
 
 document.write ("<br>");
 
 document.write (case2*mul);
 document.write ("<br>");
 document.write (case3*mul);
}


sayHello();