JavaScript

To run a node environment:

docker run -it node node
>

Strings and Variables

Set a variable test:

> var test = 'ok';
> console.log(test);
ok

With var you can overwrite the value:

> var test = 'ok';
> var test = 'ok2';
> console.log(test);
ok2

With const you cannot as the value remains what it was set initially to:

> const test = 'ok';
> const test = 'ok';
Uncaught SyntaxError: Identifier 'test' has already been declared

String interpolation:

> const name = 'ruan';
> var msg = `my name is ${name}`
> console.log(msg);
my name is ruan

With new line characters:

> var msg = `my name is:\n- ${name}`
> console.log(msg);
my name is:
- ruan

Arrays

Define array:

> var dict = [];

Append dictionary to array:

> dict.push({
    key:   "name",
    value: "ruan"
});

Print the array:

> console.log(dict);
[ { key: 'name', value: 'ruan' } ]

IF Statements

If, else and else if:

> var x = 2;
> if (x == 0) {
  console.log('x is 0');
  } else if (x > 1) {
  console.log('x is more than 1');
  } else {
  console.log('x is probably 1');
}
x is more than 1

If statement using multiple conditions:

> var event = {'name': 'ruan', 'surname': 'bekker', 'age': 34, 'severity': 'Low', 'skip': false}
> if ((!event.skip && event.name == 'ruan')) {
  console.log('true');
}
true

The same as above, but adding OR:

> var event = {'name': 'ruan', 'surname': 'bekker', 'age': 34, 'severity': 'Low', 'skip': false}
> if ((!event.skip && event.name == 'frank') || (!event.skip && event.age == 34)) {
  console.log('true');
}
true

Or it can be written like this:

> var event = {'name': 'ruan', 'surname': 'bekker', 'age': 34, 'severity': 'Low', 'skip': false}
> if (!event.skip && (event.name == 'frank') || (event.age == 34)) {
  console.log('true');
}
true

Read file contents

> const fs = require('fs');
> const fileName = "/tmp/foo-bar";
> const myText = fs.readFileSync(fileName, "utf-8");
> console.log(myText);
hello