基本类型:如string | null,适用于任何可能为空的基本类型。 对象类型:如{ name: string } | null,适用于可能为空的对象。 数组类型:如Array<string> | null,适用于可能为空的数组。 应用场景包括但不限于: 用户输入处理:用户可能不输入某些信息。
While writing a program or any script or any piece of frontend code in Javascript, if you want to check if an array is empty or not, you can use the length property of arrays in Javascript. The length property of the array returns the count of the number of elements stored in the ...
JavaScript recognizes false, 0, -0, 0n, "", null, undefined, and NaN as falsy.To verify that all values in an array are falsy, you can again use the every() method, but this time with a function that checks for falsy values:...
JavaScript Code: // Function to check if the input is an arrayvaris_array=function(input){// Using toString method to get the class of the input and checking if it is "[object Array]"if(toString.call(input)==="[object Array]")// Return true if the input is an arrayreturntrue;// ...
To check if a JavaScript array is empty or not, you can make either of the following checks (depending on your use case): const empty = !Array.isArray(array) || !array.length; const notEmpty = Array.isArray(array
Checks if value is classified as an Array object. constarray=['🍝','🍜','🍲'];constnotArray='not array';_.isArray(array);// true_.isArray(notArray);// false Underscore Returns true if object is an Array. constarray=['🍝','🍜','🍲'];constnotArray='not array';_.isArr...
JavaScript Code: // Define a function named first_last_1 with a parameter numsfunctionfirst_last_1(nums){// Calculate the index of the last element in the arrayvarend_pos=nums.length-1;// Check if the first or last element in the array is equal to 1, and return the resultreturnnums...
JS type check (TypeScript supported) functions like `isPlainObject() isArray()` etc. A simple & small integration. javascript typescript typechecker check-type javascript-type primitive-types plain-object plain-objects class-instance class-identifier type-checking type-checker type-check define-type ...
check.any(results): Returnstrueif any result value is true in an array or object returned bymap. Some examples check.even(3);// Returns false check.not.even(3);// Returns true check.maybe.even(null);// Returns true check.assert.even(3);// Throws `new TypeError('assert failed: expec...
Array= a[followed by exactly oneTypesfollowed by a]- eg.[Boolean],[Boolean | Null] Guide type-checkusesObject.toStringto find out the basic type of a value. Specifically, {}.toString.call(VALUE).slice(8,-1){}.toString.call(true).slice(8,-1)// 'Boolean' ...