Add support for $pull update operator

README.md

@@ -83,7 +83,7 @@ The following expression operators are supported: `$literal`, `$add`, `$subtract
 
 ### Update Operators
 
-The following update operators are supported: `$set`, `$unset`, `$rename`, `$inc`, `$mul`, `$min`, `$max`, `$push`, and `$pop`.
+The following update operators are supported: `$set`, `$unset`, `$rename`, `$inc`, `$mul`, `$min`, `$max`, `$push`, `$pop`, and `$pull`.
 
 ### Group Operators
 

src/update.js

@@ -5,6 +5,7 @@ const {
     modify,
     remove1,
     rename,
+    equal,
     unknownOp,
     getIDBError
 } = require('./util.js');
@@ -51,7 +52,7 @@ const compareOp = (fn) => (path_pieces, value) => {
 };
 
 const $min = compareOp((a, b) => a < b);
-const $max = compareOp((a, b) => a >  b);
+const $max = compareOp((a, b) => a > b);
 
 const $push = (path_pieces, value) => {
     const update = (obj, field) => {
@@ -85,6 +86,16 @@ const $pop = (path_pieces, direction) => {
     };
 };
 
+const $pull = (path_pieces, value) => (doc) => {
+    get(doc, path_pieces, (obj, field) => {
+        const elements = obj[field];
+        if (!Array.isArray(elements)) { return; }
+
+        const filterFn = el => !equal(el, value);
+        obj[field] = elements.filter(filterFn);
+    });
+};
+
 const ops = {
     $set,
     $unset,
@@ -94,7 +105,8 @@ const ops = {
     $min,
     $max,
     $push,
-    $pop
+    $pop,
+    $pull
 };
 
 const build = (steps, field, value) => {

test/update.js

@@ -222,7 +222,7 @@ describe('$push', () => {
 });
 
 describe('$pop', () => {
-    it('should remove a value of an array', (done) => {
+    it('should remove the first or last element of an array', (done) => {
         update({
             $pop: { a: 1, n: -1 }
         }, {
@@ -234,3 +234,17 @@ describe('$pop', () => {
         }, done);
     });
 });
+
+describe('$pull', () => {
+    it('should remove instances of a value from an array', (done) => {
+        update({
+            $pull: { a: 4 }
+        }, {
+            k: 3,
+            t: 4,
+            a: [3],
+            n: [8, 2],
+            m: { x: 80 }
+        }, done);
+    });
+});