Strings

Question 1

alert( My\n.length ); // returns and why?

Answer 1

3

Note that \n is a single “special” character, so the length is indeed 3.

Question 2

let str = Hello;

alert( str[-2] ); //

Answer 2

undefined

Question 3

let str = Hello;

alert( str[0] ); // returns?

Answer 3

H

Question 4

let str = Hello;

// the first character
alert( CODE HERE ); // H
alert( CODE HERE ); // H

Answer 4

str[0]
str.at(0)

Question 5

let str = Hello;

// the last character
alert( ); // o
alert( );

Answer 5

str[str.length - 1]
str.at(-1)

Question 6

how to iterate through “hello”
use for..of

Answer 6

for (let char of “Hello”) {
alert(char);
}

Question 7

let str = ‘Hi’;
str[0] = ‘h’; // error
alert( str[0] ); // doesn’t work

how to fix

Answer 7

str = ‘h’ + str[1]; // replace the string

Question 8

change to upper or lower case

Answer 8

.toUpperCase()
.toLowerCase()

Question 9

It looks for the substr in str, starting from the given position pos, and returns the position where the match was found or -1 if nothing can be found.

Answer 9

str.indexOf()

Question 10

let str = ‘Widget with id’;

alert( str.indexOf(‘widget’) ); //

Answer 10

-1, not found, the search is case-sensitive

Question 11

let str = ‘Widget with id’;

alert( str.indexOf(‘id’, 2) ) //

Answer 11

12

Question 12

alert(‘interface’ ); //
change first i to lower case

Answer 12

‘Interface’[0].toLowerCase()

Question 13

let str = “Widget with id”;

if (str.indexOf(“Widget”)) {
alert(“We found it”); // doesn’t work!
}

how to fix?

Answer 13

let str = “Widget with id”;

if (str.indexOf(“Widget”) != -1) {
alert(“We found it”); // works now!
}

The alert in the example above doesn’t show because str.indexOf(“Widget”) returns 0 (meaning that it found the match at the starting position). Right, but if considers 0 to be false.
So, we should actually check for -1, like this:

Question 14

The more modern method ________returns true/false depending on whether str contains substr within.

Answer 14

str.includes(substr, pos)

Question 15

alert( “Widget” );
// true, “Widget” starts with “Wid”

alert( “Widget” );
// true, “Widget” ends with “get”

Answer 15

.startsWith(“Wid”)

.endsWith(“get”)

Question 16

There are 3 methods in JavaScript to get a substring:

Answer 16

substring, substr and slice.

Question 17

Returns the part of the string between start and end (not including end). This is almost the same as slice, but it allows start to be greater than end (in this case it simply swaps start and end values).

Answer 17

str.substring(start [, end])

Question 18

let str = “stringify”;
alert( str.slice(0, 5) ); //returns

Answer 18

‘strin’, the substring from 0 to 5 (not including 5)

Question 19

let str = “stringify”;
alert( str.slice(0, 1) ) // returns

Answer 19

; // ‘s’, from 0 to 1, but not including 1, so only character at 0

Question 20

let str = “stringify”;
alert( str.slice(2) ); //

Answer 20

‘ringify’, from the 2nd position till the end
If there is no second argument, then slice goes till the end of the string:

Question 21

let str = “stringify”;
alert( str.slice(2, 6) );

Answer 21

// “ring”

Question 22

Returns the part of the string from start, with the given length

Answer 22

str.substr(start [, length])