up

1-js/06-advanced-functions/06-function-object/2-counter-inc-dec/_js.view/solution.js

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+function makeCounter() {
+  let count = 0;
+
+  function counter() {
+    return count++;
+  }
+
+  counter.set = value => count = value;
+
+  counter.decrease = () => count--;
+
+  return counter;
+}

1-js/06-advanced-functions/06-function-object/2-counter-inc-dec/_js.view/source.js

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+function makeCounter() {
+  let count = 0;
+
+  // ... your code ...
+}
+
+let counter = makeCounter();
+
+alert( counter() ); // 0
+alert( counter() ); // 1
+
+counter.set(10); // set the new count
+
+alert( counter() ); // 10
+
+counter.decrease(); // decrease the count by 1
+
+alert( counter() ); // 10 (instead of 11)

1-js/06-advanced-functions/06-function-object/2-counter-inc-dec/_js.view/test.js

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+describe("counter", function() {
+
+  it("increases from call to call", function() {
+
+    let counter = makeCounter();
+
+    assert.equal( counter(), 0 ); 
+    assert.equal( counter(), 1 ); 
+    assert.equal( counter(), 2 ); 
+  });
+
+  
+  describe("counter.set", function() {
+    it("sets the count", function() {
+
+      let counter = makeCounter();
+
+      counter.set(10);
+
+      assert.equal( counter(), 10 ); 
+      assert.equal( counter(), 11 ); 
+    });
+  });
+  
+  describe("counter.decrease", function() {
+    it("decreases the count", function() {
+
+      let counter = makeCounter();
+
+      counter.set(10);
+
+      assert.equal( counter(), 10 ); 
+
+      counter.decrease();
+
+      assert.equal( counter(), 10 ); 
+
+    });
+  });
+
+});

1-js/06-advanced-functions/06-function-object/2-counter-inc-dec/solution.md

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+
+The solution uses `count` in the local variable, but addition methods are written right into the `counter`. They share the same outer lexical environment and also can access the current `count`.

1-js/06-advanced-functions/06-function-object/2-counter-inc-dec/task.md

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+importance: 5
+
+---
+
+# Set and decrease for counter
+
+Modify the code of `makeCounter()` so that the counter can also decrease and set the number:
+
+- `counter()` should return the next number (as before).
+- `counter.set(value)` should set the `count` to `value`.
+- `counter.decrease(value)` should decrease the `count` by 1.
+
+See the sandbox code for the complete usage example.
+
+P.S. You can use either a closure or the function property to keep the current count. Or write both variants.