ok

1-js/4-object-basics/03-object-methods/7-calculator/_js.view/solution.js

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+let calculator = {
+  sum() {
+    return this.a + this.b;
+  },
+
+  mul() {
+    return this.a * this.b;
+  },
+
+  read() {
+    this.a = +prompt('a?', 0);
+    this.b = +prompt('b?', 0);
+  }
+};

1-js/4-object-basics/03-object-methods/7-calculator/_js.view/test.js

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+
+
+describe("calculator", function() {
+  
+  context("when 2 and 3 entered", function() {
+    beforeEach(function() {
+      sinon.stub(window, "prompt");
+
+      prompt.onCall(0).returns("2");
+      prompt.onCall(1).returns("3");
+
+      calculator.read();
+    });
+
+    afterEach(function() {
+      prompt.restore();
+    });
+
+    it("the sum is 5", function() {
+      assert.equal(calculator.sum(), 5);
+    });
+
+    it("the multiplication product is 6", function() {
+      assert.equal(calculator.mul(), 6);
+    });
+  });
+
+});

1-js/4-object-basics/03-object-methods/7-calculator/solution.md

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+
+
+```js run demo
+let calculator = {
+  sum() {
+    return this.a + this.b;
+  },
+
+  mul() {
+    return this.a * this.b;
+  },
+
+  read() {
+    this.a = +prompt('a?', 0);
+    this.b = +prompt('b?', 0);
+  }
+};
+
+calculator.read();
+alert( calculator.sum() );
+alert( calculator.mul() );
+```
+

1-js/4-object-basics/03-object-methods/7-calculator/task.md

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+importance: 5
+
+---
+
+# Create a calculator
+
+Create an object `calculator` with three methods:
+
+- `read()` prompts for two values and saves them as object properties.
+- `sum()` returns the sum of saved values.
+- `mul()` multiplies saved values and returns the result.
+
+```js
+let calculator = {
+  // ... your code ...
+};
+
+calculator.read();
+alert( calculator.sum() );
+alert( calculator.mul() );
+```
+
+[demo]
+