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<spanstyle="font-size: 1rem; border-bottom: 1pxsolidgrey;"> Updated June 22, 2023 </span>
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<spanstyle="font-size: 1rem; border-bottom: 1pxsolidgrey;"> Updated July 19, 2023 </span>
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In this article, we will cover a range of JavaScript interview questions, including those related to the latest versions of the language (ES6, ES7, ES8, and ES9).
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Hence, the correct answer is C: 3.
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</details>
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<details>
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<summary>
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<h3>41. What will be the output of the following code snippet?</h3>
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```javascript
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let x =10;
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functionouter() {
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console.log(x);
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if (false) {
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var x =20;
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}
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}
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outer();
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```
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- A: 10
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- B: 20
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- C: undefined
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- D: ReferenceError
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</summary>
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Answer:
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C: undefined
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In this code snippet, there's a variable hoisting issue with the var declaration inside the outer function. The variable x is declared using var within the outer function scope.
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When the function outer() is called, the console.log(x) statement is executed. At this point, the variable x is hoisted to the top of the function scope and is initialized with undefined. This means that the local variable x inside the function is different from the global x.
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The if (false) block will not be executed, so the assignment var x = 20; will not take place.
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Thus, the console.log(x) statement inside the outer function will log the value of the locally hoisted variable x, which is undefined.
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Hence, the correct answer is C: undefined.
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</details>
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<details>
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<summary>
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<h3>42. What will be the output of the following code snippet?</h3>
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```javascript
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constobj= {
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a:1,
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b:2,
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c: {
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a:3,
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b:4,
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},
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};
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const {
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a,
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c: { a:nestedA },
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} = obj;
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console.log(a, b, nestedA);
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```
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- A: 1 2 3
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- B: 1 2 4
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- C: 3 2 1
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- D: SyntaxError
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</summary>
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Answer:
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A: 1 2 3
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This code snippet uses destructuring assignment to extract values from the `obj` object. It extracts the properties `a`, `b`, and the nested property `a` from the `c` object and assigns them to the corresponding variables `a`, `b`, and `nestedA`, respectively.
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After destructuring, the variables will hold the following values:
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- `a`: 1 (value of `obj.a`)
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- `b`: 2 (value of `obj.b`)
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- `nestedA`: 3 (value of `obj.c.a`)
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When `console.log(a, b, nestedA)` is executed, it will print `123`, as the values of the variables match the above assignments.
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Hence, the correct answer is A: 1 2 3.
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</details>
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<details>
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<summary>
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<h3>43. What will be the output of the following code snippet?</h3>
This code snippet demonstrates the use of a generator function. When a generator function is called, it returns an iterator object, which can be used to control the execution of the generator function.
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The `generatorFunction` is a generator function that yields three values: `1`, `2`, and `3`. The `yield` keyword pauses the execution and returns the yielded value. When the generator is finished, it returns the value using the `return` statement.
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When the generator is executed step by step using `generator.next()`, it proceeds through the generator function's code, stopping at each `yield` statement.
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- The first call to `generator.next()` will return `{ value:1, done:false }`, indicating that the first value yielded is `1`, and the generator is not yet done.
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- The second call to `generator.next()` will return `{ value:2, done:false }`, indicating that the second value yielded is `2`, and the generator is not yet done.
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- The third call to `generator.next()` will return `{ value:3, done:true }`, indicating that the third value yielded is `3`, and the generator is done (`done` is `true`).
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After the generator is done, any further calls to `generator.next()` will keep returning `{ value:undefined, done:true }`.
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