JavaScript
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```javascript []\n/**\n * @param {Array<Function>} functions\n * @return {Promise<any>}\n */\nvar promiseAll = function(functions) {\n     return new Promise(function(resolve, reject) {\n    let count = 0;\n    let res = new Array(functions.length);\n\n    for (let i = 0; i < functions.length; i++) {\n      let fn = functions[i];\n      fn()\n        .then(function(val) {\n          count += 1;\n          res[i] = val;\n          if (count === functions.length) resolve(res);\n        })\n        .catch(function(err) {\n          reject(err);\n        });\n    }\n  });\n};\n\n/**\n * const promise = promiseAll([() => new Promise(res => res(42))])\n * promise.then(console.log); // [42]\n */\n```
['JavaScript']