## Are you ready?

**18 questions** to solve

Instructions

- This quiz goes to full-screen once you press the Start button.
- At the end of the quiz, you are able to review all the questions that you answered wrong and see their explanations.

What does

`num.toPrecision(3)`

round `num`

to?The

`toPrecision()`

method converts a number to a given amount of significant digits. Hence, in this case, `num.toPrecision(3)`

rounds `num`

to 3 s.f. This goes with choice (B). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = 38.6;
console.log(num.toPrecision(2));
```

Rounding

`38.6`

to 2 s.f. gives us the number `39`

. This is returned in the form of a string i.e. `'39'`

. Hence, the correct choice is (B). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = 50.2;
console.log(num.toPrecision(4));
```

Rounding

`50.2`

to 4 s.f. gives us the number `50.20`

. This is returned in the form of a string i.e. `'50.20'`

. Hence, the correct choice is (C). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = 123;
console.log(num.toPrecision(1));
```

Rounding

`123`

to 1 s.f. gives us the number `100`

. Since, the number `123`

has more than 1 digit in its integral part, the return value of `toPrecision()`

is in exponential form. That is, instead of `'100'`

, `'1e+2`

is returned. Hence, the correct choice is (C). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = 123;
console.log(num.toPrecision(2));
```

Rounding

`123`

to 2 s.f. gives us the number `120`

. Since, the number `123`

has more than 2 digits in its integral part, the return value of `toPrecision()`

is in exponential form. That is, instead of `'120'`

, `'1.2e+2`

is returned. Hence, the correct choice is (C). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = -1234.56;
console.log(num.toPrecision(5));
```

Rounding

`-1234.56`

to 4 s.f. gives us the number `-1234.6`

. Hence, the correct choice is (B). For more details, refer to JavaScript Number Methods — `toPrecision()`

.What does the following code log?

```
var num = 15;
console.log(num.toPrecision());
```

Without an argument, the

`toPrecision()`

method throws an error. This is exactly what happens in the code above. Hence, the correct choice is (D). For more details, refer to JavaScript Number Methods — `toPrecision()`

.The return value of

`toFixed(2)`

is the same as that of `toPrecision(2)`

for the number `0.5`

. Yes or no?For the number

`0.5`

, `toFixed(2)`

returns `'0.50'`

, and `toPrecision(2)`

also returns `'0.50'`

. They both return the same value back. Hence, the correct choice is (A). For more details, refer to JavaScript Number Methods.The invocation

`toFixed(1)`

is the same as `toPrecision(2)`

for the number `5`

. Yes or no?For the number

`5`

, `toFixed(1)`

returns `'5.0'`

, and `toPrecision(2)`

also returns `'5.0'`

. They both return the same value back. Hence, the correct choice is (A). For more details, refer to JavaScript Number Methods.The invocation

`toFixed(1)`

is the same as `toPrecision(2)`

for the number `10`

. Yes or no?For the number

`10`

, `toFixed(1)`

returns `'10.0'`

, and `toPrecision(2)`

returns `'10'`

. The return value of both the methods is not the same in this case. Hence, the correct choice is (B). For more details, refer to JavaScript Number Methods.What does the following code log?

```
var num = 16;
console.log(num.toFixed(2));
```

The

`toFixed()`

method converts a number into fixed-point notation having a given amount of decimal places. In this case, `num.toFixed(2)`

converts `16`

to `'16.00'`

. This goes with choice (D). For more details, refer to JavaScript Number Methods — `toFixed()`

.What does the following code log?

```
var num = 123;
console.log(num.toFixed(-1));
```

Calling

`toFixed()`

with a negative argument is invalid, and leads to an error.. Hence, in this case, the correct choice is (D). For more details, refer to JavaScript Number Methods — `toFixed()`

.What does the following code log?

```
var num = 100.1806;
console.log(num.toFixed(3));
```

In this case,

`toFixed(3)`

rounds `num`

to 3 decimal places, i.e. `100.181`

, and returns back the result in the form of a string, i.e. `'100.181'`

. This goes with choice (B). For more details, refer to JavaScript Number Methods — `toFixed()`

.What does the following code log?

`console.log(-3.14.toFixed(3));`

Owing to operator precedence, the

`-`

operator is evaluated last in the code above. First `3.14.toFixed(3)`

is evaluated. This returns `'3.140'`

. Then the `-`

operator converts this string into a number and negates its sign. This gives the number `-3.14`

. Hence, the correct choice is (A). For more details, refer to JavaScript Number Methods — `toFixed()`

.What does the following code log?

```
var num = 106;
console.log(num.toExponential(1));
```

`toExponential()`

converts a number into scientific notation with given digits in the fractional part, and then returns the result in the form of a string. In this case, `num.toExponential(1)`

converts `num`

to `'1.1e+2'`

(having 1 digit after the decimal point). For more details, refer to JavaScript Number Methods — `toExponential()`

.What does the argument to the number method

**specify?**`toString()`

The number method

`toString()`

accepts an optional argument which specifies the **to which convert the given number to. This goes with choice (A). For more details, refer to JavaScript Number Methods —***base*`toString()`

.What does the following code log?

`console.log(10 .toString(16));`

Called on the number

`10`

, `toString(16)`

converts it into hexadecimal representation. Since in hexadecimal, 10 is denoted as *'A'*(or even as*), the method returns*`'a'`

`'a'`

. Hence, the correct choice is (C). For more details, refer to JavaScript Number Methods — `toString()`

.What does the following code log?

`console.log( parseInt(100 .toString(2), 2) );`

`100 .toString(2)`

converts `100`

into binary representation, and then `parseInt()`

, with the second argument as `2`

, converts this binary string back into a decimal notation. That is, we get the number `100`

back in the end. Likewise, the correct choice is (B). For more details, refer to JavaScript Number Methods — `toString()`

.