判断一个数字是否为质数

function IsTrue(num){var arr = [];if(typeof num != 'number'){return false;}if(num in arr){return false;}if(num === 2){arr.push(num);return true;}else if(num%2 === 0){return false;}if(Number.isInteger(Math.sqrt(num))){return false;}for(var i = 3; i<num; i++){if(num%i === 0){return false;}}arr.push(num);return true;}


判断一个数字是否是整数方法：Number.isInteger(num);
开根号方法：Math.sqrt(num)