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质数，只能被自己和1整除的整数。

判断要点1：质数数组默认为[2]， n若能被任意质数数组中的值整除，则不是质数

(function displayPrime() {

let primeArray = [2];

for (let i=3; i< 10000; i++) {

let iIsPrime = true;

for (let prime of primeArray) {

if (i % prime === 0) {

iIsPrime = false;

break;

}

}

if (iIsPrime) {

primeArray.push(i);

}

}

console.info(primeArray);

})();

判断要点2：偶数一定不是质数

(function displayPrime() {

let time1=(new Date()).valueOf();

let primeArray = [2];

for (let i=3; i< 10000; i+=2) {

let iIsPrime = true;

for (let prime of primeArray) {

if (i % prime === 0) {

iIsPrime = false;

break;

}

}

if (iIsPrime) {

primeArray.push(i);

}

}

console.log('timeout: '+ ((new Date()).valueOf() - time1))

console.info(primeArray);

}());

判断要点3：开平方的结果是整数的整数不是质数

(function displayPrime() {

let time1=(new Date()).valueOf();

let primeArray = [2];

for (let i=3; i< 10000; i+=2) {

let sqrt=Math.sqrt(i), borderNum = i%sqrt;

let iIsPrime = !(borderNum === 0 );

if (!iIsPrime) {

continue;

}

for (let prime of primeArray) {

if (i % prime === 0) {

iIsPrime = false;

break;

}

}

if (iIsPrime) {

primeArray.push(i);

}

}

console.log('timeout: '+ ((new Date()).valueOf() - time1))

console.info(primeArray);

}());