Month: August 2022

(Solved) Why can templates only be implemented in the header file?

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Caveat: It is not necessary to put the implementation in the header file, see the alternative solution at the end of this answer. Anyway, the reason your code is failing is that, when instantiating a template, the compiler creates a new class with the given template argument. For example: template<typename T> struct Foo { T … Read more

(Solved) How can I access and process nested objects, arrays, or JSON?

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Preliminaries JavaScript has only one data type which can contain multiple values: Object. An Array is a special form of object. (Plain) Objects have the form {key: value, key: value, …} Arrays have the form [value, value, …] Both arrays and objects expose a key -> value structure. Keys in an array must be numeric, … Read more

(Solved) How to check whether a string contains a substring in JavaScript?

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ECMAScript 6 introduced String.prototype.includes: const string = “foo”; const substring = “oo”; console.log(string.includes(substring)); // true includes doesn’t have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: var string = “foo”; var substring = “oo”; console.log(string.indexOf(substring) !== -1); // true 6 solved How to check whether … Read more

(Solved) UTF-8 all the way through

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Data Storage: Specify the utf8mb4 character set on all tables and text columns in your database. This makes MySQL physically store and retrieve values encoded natively in UTF-8. Note that MySQL will implicitly use utf8mb4 encoding if a utf8mb4_* collation is specified (without any explicit character set). In older versions of MySQL (< 5.5.3), you’ll … Read more

(Solved) var functionName = function() {} vs function functionName() {}

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The difference is that functionOne is a function expression and so only defined when that line is reached, whereas functionTwo is a function declaration and is defined as soon as its surrounding function or script is executed (due to hoisting). For example, a function expression: // TypeError: functionOne is not a function functionOne(); var functionOne … Read more

(Solved) How to fix “Headers already sent” error in PHP

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No output before sending headers! Functions that send/modify HTTP headers must be invoked before any output is made. summary ⇊ Otherwise the call fails: Warning: Cannot modify header information – headers already sent (output started at script:line) Some functions modifying the HTTP header are: header / header_remove session_start / session_regenerate_id setcookie / setrawcookie Output can … Read more

(Solved) How to fix “Headers already sent” error in PHP

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Introduction Headers already sent error is a common issue encountered by PHP developers. This error occurs when the server sends the response to the browser before the header information is sent. This can be caused by a number of things, such as extra whitespace, incorrect line endings, or even a missing semicolon. Fortunately, this error … Read more

(Solved) Is Java “pass-by-reference” or “pass-by-value”?

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Introduction Java is a popular programming language used by developers around the world. One of the most common questions asked about Java is whether it is a “pass-by-reference” or “pass-by-value” language. This article will explain the difference between the two and provide an answer to the question. It will also discuss the implications of the … Read more