如何不使用loop循环,创建一个长度为100的数组,并且每个元素的值等于它的下标

  • 2016-08-18
  • 0

知乎下一个提问炸出一堆见所未见的答案,当然,是我学识浅薄了。

Object.keys(Array.apply(null,{length:100}));
//or
Object.keys(new Int8Array(100));
//or   
Object.keys(String(Array(101)));

Array.from({length:100},(v,k)=>k);
//or
Array.from(Array(100), (v,k)=>k);

Array.from(Array(100).keys());

[...Array(100).keys()];

⑤ 这个略微惊叹:

Number.prototype[Symbol.iterator] = function() {
    return {
        v: 0,
        e: this,
        next() {
            return {
                value: this.v++,
                done: this.v > this.e
            }
        }
    }
}
[...100];

⑥生成器+递归

function* angry(i){
  yield i;
  if (i < 99) { yield* angry(i + 1); }
};
Array.from(angry(0));

⑦递归

(function wallace(i) { return (i < 0) ? [] : wallace(i - 1).concat(i); })(99);

⑧尾递归

(function mistake(i, acc) { return (i < 100) ? mistake(i + 1, acc.concat(i)) : acc; })(0, []);

⑨计时器都想到了

var i = 0;
var a = [];
var timer = setInterval(function () {
  a[i] = i++;
  if (i >= 100) {
    clearInterval(timer);
    console.log(a);
  }
}, 1);

//or

var a = [];
var i = 0;
function step(timestamp) { 
  if (i < 100) {
    a[i] = i++;
    requestAnimationFrame(step);
  } else {
    console.log(a);
  }
}
requestAnimationFrame(step);

new Array(101).join('a')
    .replace(/a/g, function (v, i) { return i + ','; })
    .split(',').splice(0, 100);

⑾ Y组合子

(function (excited) {
    return function (f) {
        return f(f);
    }(function (f) {
        return excited(function (x) { return (f(f))(x); });
    });
})(function (excited) {
    return function (i) {
        return (i < 0) ? [] : excited(i - 1).concat(i);
    }
})(99);

最后是大杀器


function VM() { this.stack = [] this.cs = [] this.pc = 0 this.ax = undefined this.bx = undefined } VM.prototype.run = function(codes) { this.cs = codes this.pc = 0 return this.interpret() } VM.prototype.interpret = function() { var vm = this var instruction = vm.cs[vm.pc] var op = instruction[0] var ops = instruction.slice(1) switch (op) { case 'jl': if (vm.ax < vm.bx) { vm.pc = ops[0] return vm.interpret() } case 'inc': vm.ax++ break case 'ld': vm[ops[0]] = ops[1] break case 'push': vm.stack.push(vm[ops[0]]) break case 'pop': vm[ops[0]] = vm.stack.pop() break case 'arr_push': vm.bx.push(vm.ax) break case 'ret': return vm.ax break default: throw 'wtf??' } vm.pc++ return vm.interpret() } function make_a_100_len_array_without_fucking_loop() { var codes = [ ['ld', 'ax', 0], // 0 ['ld', 'bx', []], // 1 ['push', 'bx'], // 2 ['push', 'ax'], // 3 ['pop', 'ax'], // 4 ['pop', 'bx'], // 5 ['arr_push'], // 6 ['inc'], // 7 ['push', 'bx'], // 8 ['push', 'ax'], // 9 ['ld', 'bx', 100],// 10 ['jl', 4], // 11 ['pop', 'bx'], // 12 ['pop', 'ax'], // 13 ['ret'] ] var vm = new VM() return vm.run(codes) } var arr = make_a_100_len_array_without_fucking_loop();
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