411 REFERENCE · Wikibooks
JavaScript/Control structures/Exercises
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Topic: Conditional Branches
1. Write a script that allows a user to type in his name (prompt). The script shall answer depending on the length of the name.
Up to 5 characters: "Hello, <name>. You have a short name."
Up to 10 characters: "Hello, <name>. You have a name with a medium length."
Greater than 10 characters: "Hello, <name>. Your name is very long."
100% "use strict";
const name = prompt("Please type your name: ");
const len = name.length;
if (len <= 5) {
alert("Hello " + name + ". Your have a short name.");
} else if (len <= 10) {
alert("Hello " + name + ". You have a name with a medium length.");
} else {
alert("Hello " + name + ". Your name is very long.");
}
2. Write a script that allows a user to type in a single character. The script shall decide whether it is a vocal ('a', 'e', 'i', 'o', 'u') or a consonant.
"You typed in the vocal: <user's input>"
"You typed in the consonant: <user's input>"
"You typed in a digit or some other character (+, -, *, ...): <user's input>"
100% "use strict";
const char = prompt("Please type a character: ");
const char2 = char.substring(0, 1).toUpperCase();
switch (char2) {
case 'A':
case 'E':
case 'I':
case 'O':
case 'U':
alert("You typed in the vocal: " + char);
break;
case 'B':
case 'C':
case 'D':
// ... all the other consonants
alert("You typed in the consonant: " + char);
break;
default:
alert("You typed in a digit or some other character: (+, -, *, ...): " + char);
break;
}
3. try / catch
Write a script that calls a functionconnectToDatabase(). This function does not exist in your script, which causes the JavaScript engine to generate a runtime error.
Catch the error and produce a meaningful error.
Terminate the script.
100% "use strict";
try {
connectToDatabase();
// ... SQL commands ...
} catch (err) {
alert("The function 'connectToDatabase()' is not known. System error?");
alert("The system error is: " + err);
} finally {
// ... show 'good by' screen
alert("Program terminates.");
}
{What is the result?
"use strict";
const x = 0;
let y = 0;
if (x < 10)
alert("One");
y = 20;
if (y === 0)
alert("Two");
|type="()"}
+ A single message
- Two messages
{What shows the 'alert' statement?
"use strict";
let x = 2;
switch (x) {
case 1:
x++;
case 2:
x++;
x++;
case 3:
x++;
x++;
x++;
default:
x = 0;
} //
alert(x);
|type="()"}
+ 0
- 2
- 4
- None of the above