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) { indices.push(idx); idx = array.indexOf(element, idx + 1); }...
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...
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 if(!Array.prototype.indexOf)Array.prototype.indexOf=function(searchValue,index){// In non-strict-mode, if the `this` variable is null// or undefined, then it is set the the window object.// Else, `this` is automaticly converted to an object.varlen=this.length>...
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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