Env

Description

The Env object provides access to the system environment variables.

It has various modes of operation, depending on how it is created/used:

• As new Env() creates a new instance with all current environment variables as properties.
  • Variables could then be accessed directly, for example:

    var env = new Env();
    console.log(env.PATH);

  • You can check if a variable exists in the usual ways of JS object properties (check if !== undefined, hasOwnProperty(), etc).
  • You can iterate over the variables as key-value pairs using a for...of loop. For example:

    var env = new Env();
    for (const [name, value] of env)
      console.log(name, "=", value);

    Or Java style:

    var it = new Env().iterator;
    while (it.hasNext()) {
      const [name, value] = it.next();
      console.log(name, "=", value);
    }

  • The variable names can be retrieved with names, the values with values and the name-value pairs with entries properties (entries is an Iteratable).
  • toString() and valueOf() return a JSON.stringify() representation of the full variables list with an indentation of 2 spaces.
• As new Env(variableName) or new Env(variableName, defaultValue) creates a new instance of a named variable, optionally with a default value.
  Eg. new Env("PATH") or new Env("MYVAR", "Not defined yet").
  • isSet returns true/false based on if the variable exists in the environment;
  • value is the current value of the variable. If the variable doesn't exist in the current environment then defaultValue used in constructor is returned, or undefined if one wasn't set.
  • name is the variable name the instance was created with.
  • isValid indicates that a variable name was specified in the constructor and is not blank.
  • set(value) sets the value if the variable in the current environment (this will create it if it doesn't exist). Returns true/false to indicate success or failure. Note that setting a variable with an undefined value will remove it from the environment (same as unset());
  • unset() removes the variable from the current environment. Returns true/false to indicate success or failure.
  • toString() and valueOf() return the variable value (same as value()).
• Static methods:
  • Env or Env.entries - Iteratable of name-value pairs of all current environment variables, eg. use in for ... of loop (see example above).
  • Env.iterator - Java style iterator of name-value pairs of all current environment variables (see example above).
  • Env.names - Array of all current environment variable names.
  • Env.values - Array of all current environment variable values.
  • Env.isSet(variableName) - returns true/false based on if the variableName exists in the environment.
  • Env.value(variableName, defaultValue) - returns the value of variableName or defaultValue if variable doesn't exist in the environment.
  • Env.set(variableName, value) - sets the value of variableName in the current environment (this will also create it if it doesn't exist). Returns true/false to indicate success or failure. Note that setting a variable with an undefined value will remove it from the environment (same as unset(variableName));
  • Env.unset(variableName) - removes variableName from the current environment. Returns true/false to indicate success or failure.

Public Member Functions
	Env ()
	Env (varName, defaultValue)
	Env (varName)

Constructor & Destructor Documentation

Env() [1/3]

Env

(

)

Creates a new instance with all current environment variables as properties.

Env() [2/3]

Env	(		varName,
			defaultValue
	)

Creates a new instance of a named variable with a default value.

The default is used if trying to get the value of this variable before it exists in the actual environment.

Env() [3/3]

Env

(

varName

)

Creates a new instance of a named variable with an undefined default value.