过去几个小时我一直试图找出如何找到2个数字之间的数组，但我不知道该往哪里去。我需要做什么？ 18和20只是占位符号，随意使用你想要的任何数字。
function start() {
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20];
var lower = 18;
var upper = 20;
if (need help here) {
alert('Yes');
} else {
alert('No');
}
document.getElementById('listOfvalues').innerHTML = ('There are ' + ___ + ' numbers that are between the two numbers);
document.getElementById('numberExist').innerHTML = numberExist;
}
我知道我没有提供太多，但如果我自己尝试这样做，我会发疯的
答案 0 :(得分：2)
var lower = 18;
var upper = 20;
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20];
var between = array.filter(function(item) {
return (item > lower && item < upper);
});
答案 1 :(得分：2)
var listOfvalues=[];
for(var i=0;i<array.length;i++){
if (array[i]>18 && array[i]<20) {
listOfvalues.push(array[i]);
}
}
document.getElementById('listOfvalues').innerHTML = 'There are ' + listOfvalues.length + ' numbers that are between the two numbers';
答案 2 :(得分：1)
一种方法如下：
// a changed (hopefully meaningful) name for the function,
// lower: Number, the lower-boundary,
// upper: Number, the upper-boundary,
// haystack: Array, the array of values:
function numbersBetween(lower, upper, haystack) {
// if every value of the Array is, or can be coerced to,
// a Number then we continue to work with that Array:
if (haystack.every(value => Number(value))) {
// Here we use Array.prototype.filter() to filter the
// values of the Array according the function:
return haystack.filter(
// here we use an Arrow function, since we don't need
// to use a 'this'; here we retain the current value ('n')
// in the Array if that Number is greater than the
// lower-boundary and lower than the upper-boundary:
n => n > lower && n < upper
);
}
// otherwise, if not every value is, or can be coerced,
// to a Number we simply return an empty Array:
return [];
}
// this caches the element with the id of 'output':
let list = document.getElementById('output'),
// we create an <li> element:
li = document.createElement('li'),
// we create a document fragment:
fragment = document.createDocumentFragment(),
// and an empty uninitialised variable:
clone;
// we call the numbersBetween function, passing in the relevant
// boundaries and the Array:
numbersBetween(7, 20, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15])
// because the function returns an Array (either an empty Array or
// an Array with values), we can chain the function using
// Array.prototype.forEach():
.forEach(
// here we use another Arrow function expression:
num => {
// clone the created <li> element and assign it
// the 'clone' variable:
clone = li.cloneNode();
// set the clone's textContent to be equal to
// the current Array-element of the Array over
// which we're iterating:
clone.textContent = num;
// and append that cloned-element to the
// document.fragment:
fragment.appendChild(clone);
});
// this could be used in the last iteration of the
// Array.prototype.forEach() method, but because it
// generates no errors (an empty document fragment
// can be appended to an element without consequence),
// we perform this step here, appending the document
// fragment to the cached 'list' element which appends
// the nodes contained within the document fragment to
// the specified parent-node (list):
list.appendChild(fragment);
function numbersBetween(lower, upper, haystack) {
if (haystack.every(value => Number(value))) {
return haystack.filter(
n => n > lower && n < upper
);
}
return [];
}
let list = document.getElementById('output'),
li = document.createElement('li'),
fragment = document.createDocumentFragment(),
clone;
numbersBetween(7, 20, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15]).forEach(
num => {
clone = li.cloneNode();
clone.textContent = num;
fragment.appendChild(clone);
});
list.appendChild(fragment);#output::before {
content: 'The following numbers were found:';
display: list-item;
list-style-type: none;
}
#output:empty::before {
content: '';
}<ul id="output"></ul>
答案 3 :(得分：0)
为Wei的回答提供过滤后的解决方案
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20];
var lower = 18;
var upper = 20;
var result = array.filter(function(item) {
return item >= lower && item <= upper;
});
document.getElementById('listOfvalues').innerHTML = ('There are ' + result.length + ' numbers that are between the two numbers);
简而言之，使用filter function根据您的低边界和高边界返回结果。打印返回的值数组的长度。
对于if / else语句，您可以自己完成。
编辑：添加了过滤器
的链接答案 4 :(得分：0)
您可以测试，如果该值在给定范围内并计算它。
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20],
lower = 18,
upper = 20,
result = array.reduce(function (r, a) {
return r + (a >= lower && a <= upper);
}, 0);
console.log(result);
ES6
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20],
lower = 18,
upper = 20,
result = array.reduce((r, a) => r + (a >= lower && a <= upper), 0);
console.log(result);
Array#reduce在这种情况下如何运作？您有一个结果的累加器，表示为
r和迭代的实际值，表示为a。如果值在给定范围内，则返回的结果是前一个计数和ckeck的总和。r a return comment ------ ------ ------ -------- 0 18 1 in range 1 23 1 1 20 2 in range 2 17 2 2 21 2 2 18 3 in range 3 22 3 3 19 4 in range 4 18 5 in range 5 20 6 in range 6 result
一些想法，都是ES6风格。
您可以使用Array#reduce的回调，其关闭超过lower和upper，例如
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20],
getCountInRange = (lower, upper) => (r, a) => r + (a >= lower && a <= upper);
console.log(array.reduce(getCountInRange(18, 20), 0));
或者您可以使用一个函数来获取数组lower和upper并返回计数。
var array = [18, 23, 20, 17, 21, 18, 22, 19, 18, 20],
getCountInRange = (array, lower, upper) => array.reduce((r, a) => r + (a >= lower && a <= upper), 0);
console.log(getCountInRange(array, 18, 20));