diff --git a/Task1.js b/Task1.js
new file mode 100644
index 0000000..13014e6
--- /dev/null
+++ b/Task1.js
@@ -0,0 +1,30 @@
+function GroupByKey(array,key)
+{
+  const tempData = {};
+
+  for ( var index=0; index<array.length; index++)
+   {
+
+    if (!tempData[array[index][key]]) 
+    {
+        tempData[array[index][key]]=[];
+    }
+
+    tempData[array[index][key]].push(array[index])
+
+  }
+  return tempData
+}
+const array=[
+    {id:1,name:"Bilal", city:"Lahore"},
+    {id:1,name:"Bilal", city:"Lahore"},
+    {id:3,name:"Hafsa", city:"Karachi"},
+    {id:4,name:"Rehan", city:"Lahore"},
+    {id:5,name:"Saqib", city:"Karachi"},
+    {id:6,name:"Farhan", city:"Islamabad"}
+
+];
+
+const key='city';
+
+console.log(GroupByKey(array,key))
\ No newline at end of file
diff --git a/Task2.js b/Task2.js
new file mode 100644
index 0000000..155c018
--- /dev/null
+++ b/Task2.js
@@ -0,0 +1,25 @@
+const array=[
+    {id:1,name:"Bilal", city:"Lahore"},
+    {id:1,name:"Bilal", city:"Lahore"},
+    {id:3,name:"Hafsa", city:"Karachi"},
+    {id:4,name:"Rehan", city:"Lahore"},
+    {id:5,name:"Saqib", city:"Karachi"},
+    {id:6,name:"Farhan", city:"Islamabad"}
+];
+const key='city';
+
+function GroupByKey(arr,key) {
+    var tempobj=[];
+    arr.reduce((accumulator,currentvalue)=>{
+        if(!accumulator[currentvalue[key]]){
+            accumulator[currentvalue[key]]=[]
+        }
+        accumulator[currentvalue[key]].push(currentvalue)
+        tempobj=accumulator
+        return accumulator
+    },{});
+    return tempobj
+    
+}
+
+console.log(GroupByKey(array,key))
diff --git a/Task3.js b/Task3.js
new file mode 100644
index 0000000..968d5e8
--- /dev/null
+++ b/Task3.js
@@ -0,0 +1,31 @@
+const array=[
+    {id:'one',next:"two", value:null},
+    {id:'two',next:"three", value:null},
+    {id:'three',next: null, value:null}
+];
+var result=[]
+
+function updatearray(arr){
+    for(var i=arr.length-1; i>-1;i--){
+        updatevalue(arr[i])
+    }
+}
+
+function updatevalue(ele){
+    if(ele.next==null){
+        return (result.unshift(ele))
+    }
+    else{
+        for(var j in array){
+            if(result[0].id==array[j].next){
+                array[j].value=result[0]
+                result.unshift(array[j])
+                break
+            }
+        }
+    }
+}
+updatearray(array)
+result=JSON.stringify(result);
+console.log(result)
+// console.log(result[0].value)
\ No newline at end of file
diff --git a/Task4.js b/Task4.js
new file mode 100644
index 0000000..109f3f2
--- /dev/null
+++ b/Task4.js
@@ -0,0 +1,29 @@
+const array=[
+    {id:'one',next:"two", value:null},
+    {id:'two',next:"three", value:null},
+    {id:'three',next: null, value:null}
+];
+var result=[]
+function updatevalue(array){
+    if(result.length==0){
+        for(var i in array){
+            if(array[i].next==null){
+                result.unshift(array[i])
+                array.splice(array[i],1)
+            }
+        }
+    }
+    for(var j in array){
+        if(result[0].id==array[j].next){
+            array[j].value=result[0]
+            result.unshift(array[j])
+            array.splice(array[j],1)
+            updatevalue(array)
+            break
+            }
+        }
+    
+}
+updatevalue(array.reverse())
+
+console.log(result)
\ No newline at end of file
diff --git a/Task5.js b/Task5.js
new file mode 100644
index 0000000..44a95ce
--- /dev/null
+++ b/Task5.js
@@ -0,0 +1,23 @@
+const array=[
+    {id:'one',next:"two", value:null},
+    {id:'two',next:"three", value:null},
+    {id:'three',next: null, value:null}
+];
+var nextindex=0
+function updatearray(array){
+    updatevalue(array,0)
+    function updatevalue(array,index){
+        if(array[index].next==null){
+            return array[index]
+        }
+        else{
+           array[index].value=updatevalue(array,index+1)
+           return array[index]
+        }
+    }
+}
+
+updatearray(array)
+var arr=array
+arr=JSON.stringify(array)
+console.log(arr)
\ No newline at end of file
diff --git a/Task6.js b/Task6.js
new file mode 100644
index 0000000..9878aa2
--- /dev/null
+++ b/Task6.js
@@ -0,0 +1,22 @@
+function delay(time) {
+  return new Promise((resolve, reject) => {
+    if (typeof(time) === 'string') {
+        console.log()
+      reject(new Error("Delay required a valid number"));
+    }
+    else{
+        time *= 1000;
+      setTimeout(resolve, time);
+    }
+  });
+}
+
+async function main() {
+  await delay(2);
+  console.log("saad");
+  await delay(2);
+  console.log("fareed");
+  await delay(2);
+  console.log("happy Birthday");
+}
+main();