不可变数据结构：ECMA 4 中的记录和元组

// creating an immutable record const kittyfacts = #{ name: "turbodog", age: 17, favoritetoy: "laser pointer" }; // accessing values console.log(kittyfacts.name); // outputs: turbodog console.log(kittyfacts.favoritetoy); // outputs: laser pointer // attempting to modify will create a new instance const updatedkittyfacts = #{ ...kittyfacts, age: 18 };console.log(kittyfacts.age); // outputs: 17 (unchanged) console.log(updatedkittyfacts.age); // outputs: 18 (new instance)

// creating an immutable tuple const concertsetlist = #[ "tupelo", "live oak", "strawberry woman", "elephant" ]; // accessing values console.log(concertsetlist[0]); // outputs: tupelo console.log(concertsetlist[2]); // outputs: strawberry woman // attempting to modify will create a new instance const updatedsetlist = #[...concertsetlist, "chaos and clothes"]; console.log(concertsetlist.length);  // outputs: 4 (unchanged) console.log(updatedsetlist.length);// outputs: 5 (new instance)

// Creating a Tuple const originalMixtape = #[ "If We Were Vampires", "World Leader Pretend", "Right Back to It" ]; // Updating a specific index const updatedMixtape = originalMixtape.with(1, "Turn You Inside-Out"); console.log(originalMixtape); // Outputs: #[ "If We Were Vampires", "World Leader Pretend", "Right Back to It" ]; console.log(updatedMixtape); // Outputs: #[ "If We Were Vampires", "Turn You Inside-Out", "Right Back to It" ];