Example used to explain pass-by-value vs. pass-by-reference and which is used in Javascript.

Function Definitions

/**
 * This function assigns a new value to the input parameter.
 */
var func1 = function func1 (param1) {
  param1 = [4, 5 ,6];
};

/**
 * This function acts on the input parameter.
 */
var func2 = function func2 (param2) {
  param2.splice(0, 3, 4, 5, 6);
};

/**
 * This function acts on the input parameter, assigns it a new value, then
 * acts on it again.
 */
var func3 = function func3 (param3) {
  param3.splice(0, 3, 4, 5, 6);
  param3 = ['a', 'b', 'c'];
  param3.splice(0, 3, 'x', 'y', 'z');
};

Functions Calls

// step 1
var x = set(); // returns [1, 2, 3]
func1(x);
log(JSON.stringify(x, null, 2));

// step 2
x = set();
func2(x);
log(JSON.stringify(x, null, 2));

// step 3
x = set();
func3(x);
log(JSON.stringify(x, null, 2));