1-JavaScript简介
312 2023-04-03 03:15:03
检测数组ages中是否有元素大于输入框输入的值:
<p>最小年龄: <input type="number" id="ageToCheck" value="18"></p><button onclick="myFunction()">点我</button><p>是否所有年龄都符号条件? <span id="demo"></span></p><script>var ages = [32, 33, 12, 40];function checkAdult(age) { return age >= document.getElementById("ageToCheck").value;}function myFunction() { document.getElementById("demo").innerHTML = ages.every(checkAdult);}</script>
var ages = [4, 12, 16, 20]; function checkAdult(age) { return age >= document.getElementById("ageToCheck").value;} function myFunction() { document.getElementById("demo").innerHTML = ages.find(checkAdult);}
some() 方法会依次执行数组的每个元素:
array.some(function(currentValue,index,arr),thisValue)
<p>最小年龄: <input type="number" id="ageToCheck" value="18"></p><button onclick="myFunction()">点我</button><p>判断结果: <span id="demo"></span></p><script>var ages = [4, 12, 16, 20];function checkAdult(age) { return age >= document.getElementById("ageToCheck").value;}function myFunction() { document.getElementById("demo").innerHTML = ages.some(checkAdult);}</script>
[1, 2, 3].includes(2); // true[1, 2, 3].includes(4); // false[1, 2, 3].includes(3, 3); // false[1, 2, 3].includes(3, -1); // true[1, 2, NaN].includes(NaN); // true
findIndex() 方法返回传入一个测试条件(函数)符合条件的数组第一个元素位置。
var ages = [4, 12, 16, 20]; function checkAdult(age) { return age >= document.getElementById("ageToCheck").value;} function myFunction() { document.getElementById("demo").innerHTML = ages.findIndex(checkAdult);}
var ages = [32, 33, 16, 40];function checkAdult(age) { return age >= 18;}function myFunction() { document.getElementById("demo").innerHTML = ages.filter(checkAdult);}
<button onclick="numbers.forEach(myFunction)">点我</button><p id="demo"></p> <script>demoP = document.getElementById("demo");var numbers = [4, 9, 16, 25]; function myFunction(item, index) { demoP.innerHTML = demoP.innerHTML + "index[" + index + "]: " + item + "<br>"; }</script>
Array.from(object, mapFunction, thisValue)
var setObj = new Set(["a", "b", "c"]);var objArr = Array.from(setObj);objArr[1] == "b"; // true
var arr = Array.from([1, 2, 3], x => x * 10);// arr[0] == 10;// arr[1] == 20;// arr[2] == 30;
var fruits = ["Banana", "Orange", "Apple", "Mango"];var energy = fruits.join();
Banana,Orange,Apple,Mango
array.map(function(currentValue,index,arr), thisValue)
var numbers = [4, 9, 16, 25];function myFunction() { x = document.getElementById("demo") x.innerHTML = numbers.map(Math.sqrt);}
2,3,4,5
数组中的每个元素乘于输入框指定的值,并返回新数组:var numbers = [65, 44, 12, 4];function multiplyArrayElement(num) { return num * document.getElementById("multiplyWith").value;}function myFunction() { document.getElementById("demo").innerHTML = numbers.map(multiplyArrayElement);}