Added position option to push and pop

louischatriot#603

Author: SReject

lib/datastore.js

@@ -576,6 +576,7 @@ class Datastore extends EventEmitter {
         const callback = cb || function () {};
         const multi = options.multi !== undefined ? options.multi : false;
         const upsert = options.upsert !== undefined ? options.upsert : false;
+        const position = options.position !== undefined ? options.position : false;
 
         async.waterfall([
             cb => {
@@ -602,7 +603,7 @@ class Datastore extends EventEmitter {
                         // updateQuery contains modifiers, use the find query as the base,
                         // strip it from all operators and update it according to updateQuery
                         try {
-                            toBeInserted = model.modify(model.deepCopy(query, true), updateQuery);
+                            toBeInserted = model.modify(model.deepCopy(query, true), updateQuery, position);
                         } catch (err) {
                             return callback(err);
                         }
@@ -638,7 +639,7 @@ class Datastore extends EventEmitter {
                                 if (this.timestampData) {
                                     createdAt = candidates[i].createdAt;
                                 }
-                                const modifiedDoc = model.modify(candidates[i], updateQuery);
+                                const modifiedDoc = model.modify(candidates[i], updateQuery, position);
                                 if (this.timestampData) {
                                     modifiedDoc.createdAt = createdAt;
                                     // modifiedDoc.updatedAt = new Date();

lib/model.js

@@ -482,7 +482,7 @@ lastStepModifierFunctions.$unset = function (obj, field) {
  * Optional modifier $slice to slice the resulting array, see https://docs.mongodb.org/manual/reference/operator/update/slice/
  * Différeence with MongoDB: if $slice is specified and not $each, we act as if value is an empty array
  */
-lastStepModifierFunctions.$push = function (obj, field, value) {
+lastStepModifierFunctions.$push = function (obj, field, value, position) {
     // Create the array if it doesn't exist
     if (!has(obj, field)) {
         obj[field] = [];
@@ -492,7 +492,7 @@ lastStepModifierFunctions.$push = function (obj, field, value) {
         throw new Error("Can't $push an element on non-array values");
     }
 
-    if (value !== null && typeof value === 'object' && value.$slice && value.$each === undefined) {
+    if (value !== null && typeof value === 'object' && value.$slice && value.$each === undefined && value.position === undefined) {
         value.$each = [];
     }
 
@@ -528,7 +528,11 @@ lastStepModifierFunctions.$push = function (obj, field, value) {
             obj[field] = obj[field].slice(start, end);
         }
     } else {
-        obj[field].push(value);
+        if (position === undefined) {
+            obj[field].push(value);
+        } else {
+            obj[field].splice(position, 0, value);
+        }
     }
 };
 
@@ -572,7 +576,7 @@ lastStepModifierFunctions.$addToSet = function (obj, field, value) {
 };
 
 /** Remove the first or last element of an array */
-lastStepModifierFunctions.$pop = function (obj, field, value) {
+lastStepModifierFunctions.$pop = function (obj, field, value, position) {
     if (!Array.isArray(obj[field])) {
         throw new Error("Can't $pop an element from non-array values");
     }
@@ -583,7 +587,9 @@ lastStepModifierFunctions.$pop = function (obj, field, value) {
         return;
     }
 
-    if (value > 0) {
+    if (position !== undefined) {
+        obj[field] = obj[field].splice(position, 1);
+    } else if (value > 0) {
         obj[field] = obj[field].slice(0, obj[field].length - 1);
     } else {
         obj[field] = obj[field].slice(1);
@@ -641,11 +647,11 @@ lastStepModifierFunctions.$min = function (obj, field, value) {
 
 // Given its name, create the complete modifier function
 function createModifierFunction (modifier) {
-    return function (obj, field, value) {
+    return function (obj, field, value, position) {
         let fieldParts = typeof field === 'string' ? field.split('.') : field;
 
         if (fieldParts.length === 1) {
-            lastStepModifierFunctions[modifier](obj, field, value);
+            lastStepModifierFunctions[modifier](obj, field, value, position);
         } else {
             if (obj[fieldParts[0]] === undefined) {
                 // Bad looking specific fix, needs to be generalized modifiers that behave like $unset are implemented
@@ -654,7 +660,7 @@ function createModifierFunction (modifier) {
                 }
                 obj[fieldParts[0]] = {};
             }
-            modifierFunctions[modifier](obj[fieldParts[0]], fieldParts.slice(1), value);
+            modifierFunctions[modifier](obj[fieldParts[0]], fieldParts.slice(1), value, position);
         }
     };
 }
@@ -665,7 +671,7 @@ Object.keys(lastStepModifierFunctions).forEach(function (modifier) {
 });
 
 /** Modify a DB object according to an update query */
-function modify (obj, updateQuery) {
+function modify (obj, updateQuery, position) {
     let keys = Object.keys(updateQuery),
         firstChars = keys.map(item => item[0]),
         dollarFirstChars = firstChars.filter(item => item === '$'),
@@ -701,7 +707,7 @@ function modify (obj, updateQuery) {
 
             const keys = Object.keys(updateQuery[m]);
             keys.forEach(function (k) {
-                modifierFunctions[m](newDoc, k, updateQuery[m][k]);
+                modifierFunctions[m](newDoc, k, updateQuery[m][k], position);
             });
         });
     }