Python Default Parameters, Rest & Spread Syntax
JavaScript parameters allow default fallback values if omitted or passed as undefined. The rest operator (...args) collects multiple arguments into an array, while the spread operator expands arrays or objects into individual elements.
"Rest parameters are like a laundry bag gathering loose socks into a single bundle (...items). Spread syntax is dumping that bag out flat on a table to inspect each sock individually."
Deep Dive: How It Works
Default Parameters: function greet(name = "Guest") prevents undefined values.
Rest Operator (...args): Must be the last parameter in the function signature and collects remaining arguments into an array.
Spread Operator (...arr): Clones or combines arrays and objects shallowly: const merged = [...a, ...b];.
Syntax Blueprint
function sum(...nums) { ... } | const combined = [...arr1, ...arr2]Use ... to gather arguments into an array or spread elements across a new structure.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Placing rest parameters before other named parameters.Why it happens: function test(...rest, last) is a syntax error because rest must be the final parameter.
How to fix: Always place ...rest as the very last item in the parameter list.
Live Interactive Example
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Merge arrays with spread syntax
- Given const core = ["CPU", "RAM"]; and const extra = ["GPU", "SSD"];
- Create const hardware = [...core, ...extra];
- Print "Hardware: CPU, RAM, GPU, SSD" using hardware.join(", ").
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