JavaScript 1999 (ES3)
ECMAScript 3 (1999)
The first revision to JavaScript.
ECMAScript 1999 is also known as ES3.
ES3 Features
| Feature | Description |
|---|---|
| Regular expressions | Sequence of characters that forms a search pattern |
| Error handling (try...catch) | Statement to define code blocks to be tested in case of an error |
| The switch keyword | Selects code blocks to be executed based on a conditions |
| The do...while loop | A variant of the while loop |
Browser Support
JavaScript 1999 is supported in all browsers:
| Chrome | IE/Edge | Firefox | Safari | Opera |
Regular Expressions
A sequence of characters that forms a search pattern.
Example
Do a case-insensitive search for "w3schools" in a string:
let text = "Visit W3Schools";
let n = text.search(/w3schools/i);
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The try...catch Keywords
Statement to define code blocks to be tested in case of an error.
Examples
You cannot use a non-existing variable:
let x = 5;
try {
x = y + 1;
} catch(err) {
let text = err.name;
}
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The switch Keyword
Based on a condition, switch selects one or more code blocks to be executed.
Example
This example uses the weekday number to calculate the weekday name:
switch (new Date().getDay()) {
case 0:
day = "Sunday";
break;
case 1:
day = "Monday";
break;
case 2:
day = "Tuesday";
break;
case 3:
day = "Wednesday";
break;
case 4:
day = "Thursday";
break;
case 5:
day = "Friday";
break;
case 6:
day = "Saturday";
}
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The do...while Loop
The do while runs at least once, even if the condition is false from the start.
This is because the code block is executed before the condition is tested:
Do not forget to increase the variable used in the condition, otherwise the loop will never end!
