The following example usesindexOfto find all the indices of an element in a given array, usingpushto add them to another array as they are found. varindices = []; varidx = array.indexOf(element); while(idx != -1
To access elements of an array using index in JavaScript, mention the index after the array variable in square brackets. The syntax to access an element from arrayarrat indexiis </> Copy arr[i] Read Array Element at Specific Index array[index], if used in an expression, or on the right...
代码语言:javascript 复制 var a = [2, 9, 9]; a.indexOf(2); // 0 a.indexOf(7); // -1 if (a.indexOf(7) === -1) { // element doesn't exist in array } 语法 代码语言:javascript 复制 arr.indexOf(searchElement[, fromIndex]) ...
我从myarray.indexOf(element) 得到 -1,即使元素似乎在 myarray 中。 下面是一些代码片段: {代码...} 警报显示 nds 确实包含 el,但警报应该只在 idx==-1 时触发,只有当 nds 不包含 el 时才会触发。 我知道我...
The findIndex() method returns the index of the first element in an array that pass a test (provided as a function).The findIndex() method executes the function once for each element present in the array:If it finds an array element where the function returns a true value, findIndex()...
TheindexOf()method returns the first index of occurance of anarrayelement, or-1if it is not found. Example letlanguages = ["Java","JavaScript","Python","JavaScript"]; // get the index of the first occurrence of "JavaScript"letindex = languages.indexOf("JavaScript"); ...
JavaScript // Create an array. var ar = ["ab", "cd", "ef", "ab", "cd"]; // Determine the first location, in descending order, of "cd". document.write(ar.lastIndexOf("cd") + ""); // Output: 4 // Find "cd" in descending order, starting at index 2. document...
indexOf() 使用严格相等(与 === 运算符使用的算法相同)将 searchElement 与数组中的元素进行比较。NaN 值永远不会被比较为相等,因此当 searchElement 为NaN 时indexOf() 总是返回 -1。 indexOf() 方法会跳过稀疏数组中的空槽。 indexOf() 方法是通用的。它只期望 this 值具有 length 属性和整数键属性。
// function that returns odd numberfunctionisOdd(element){returnelement %2!==0; }// defining an array of integersletnumbers = [2,8,1,3,4]; // returns the index of the first odd number in the arrayletfirstOdd = numbers.findIndex(isOdd); ...
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