轉載—–javascript quiz

問題很容易看懂，所以就沒有翻譯.

------------------------原文--------------------------------

## Intro Questions

　　01. When might comparative type coercion occur? How would you avoid it? How would you change a "falsy" or "truthy" value into a real boolean?

　　02. Describe how variable scope works. Explain how to create a closure using a self-executing anonymous function (also called IIFE: immediately-invoked function expression).

　　03. Explain briefly how prototypal inheritance differs from class-based, "classical" inheritance.

　　04. Describe how the "module pattern" works. Explain how the "revealing module pattern" expands upon it.

　　05. How does a client-side MVC (or MVVM) approach work? What is your preferred MV* JS framework?

## Additional Questions

　　06. Why do these yield different results?

```js
'1' + 2 + 3 ; // Equals '123'
3 + 2 + '1'; // Equals '51'
3 + 2 + 1 ; // Equals 6
```

　　07. Why is `0.3` *not* the result of the following addition? How do you work around this peculiarity?

```js
0.1 + 0.2; // Equals 0.30000000000000004
```

　　08. Describe how variable hoisting works, and how to avoid bugs that may arise from it.

　　09. How do these differ?

```js
function foo() {}

// versus

var foo = function() {};
```

　　10. When might you use a function's `call()` method, or its `apply()` method?

　　11. Explain how to determine if a variable is an array or an object. (*Hint:* `typeof` lies!)

　　12. In the following example, what is foo aliased to? (*Hint:* It is what `this` means.)

```js
(function(foo) {
// What is 'foo' aliased to?
})(this);
```

　　13. In JavaScript (and the DOM), some global variables are actually mutable, such as: `window`, `document`, and `undefined`. How would you write code to ensure these were predictably available for use? Assuming someone had injected this code, how would you work around it? (*Hint:* See the previous question.)

```js
var window = '';
var document = 0;
var undefined = true;
```

　　14. In one line of code, how you would make a copy of an array?

　　15. What is the difference between `setInterval` and `setTimeout`? *Bonus:* What is the lowest cross-browser increment that each can accurately use?

　　16. Explain how `delete` works. What types of things cannot be deleted?

　　17. Describe how event delegation works, and when you should use it to handle UI interaction. Example markup…

```html
<ul id="special">
<li>
<a href="#">Special link 1</a>
</li>
<li>
<a href="#">Special link 2</a>
</li>
<li>
<a href="#">Special link 3</a>
</li>
</ul>
```

　　18. What does this snippet of code do?

```js
var foo = bar ? bar : 0;
```

　　19. When might you write something like this, and what is it shorthand for?

```js
foo && foo.bar();
```

　　20. How do `parseInt` and `parseFloat` differ? When would you use a number's `toFixed()` method? In what instance might the following code snippet actually make sense to use?

```js
var my_number = my_string - 0;
```

　　21. Write a function named `sum` that returns the total of any number of parameters. Example&hellip;

```js
// Should equal 15
sum(1, 2, 3, 4, 5);

// Should equal 0
sum(5, null, -5);

// Should equal 10
sum('1.0', false, 1, true, 1, 'A', 1, 'B', 1, 'C', 1, 'D', 1, 'E', 1, 'F', 1, 'G', 1);

// Should equal 0.3, not 0.30000000000000004
sum(0.1, 0.2);
```

ANSWERS：http://www.cnblogs.com/chenguangyin/archive/2012/11/24/2786129.html

　　原文地址：https://github.com/nathansmith/javascript-quiz