Variable

A variable is a name that refers to a value stored in memory. You assign a value to it, read it later by name and, unless it is declared constant, replace it with a different value.

Why it matters

Variables are the basic building block of every program. Good names make code self-explanatory, and a variable's scope, the part of the program where it is visible, determines what can change it. Many bugs come from a variable holding a value other than what the programmer expected.

Example

const taxRate = 0.18;       // constant: cannot be reassigned
let total = 0;              // can change
total = total + 100 * (1 + taxRate);
console.log(total);         // 118

taxRate is declared with const, so reassigning it raises an error, while total is declared with let and updated.

Common mistakes

• Using vague names like x or data for values with real meaning.
• Relying on global variables that any function can modify.
• Mixing up the value with a reference; in many languages two variables can point to the same list or object.

Related

• Function
• Data structure
• Environment variable
• Object-oriented programming

यह पेज सामान्य जानकारी है, जिसे हमारी संपादकीय टीम ने लिखा है और दस्तावेज़ीकरण बदलने पर अपडेट किया जाता है। सर्वर और प्रदाता अलग-अलग होते हैं, इसलिए बदलाव पहले सुरक्षित तरीके से जाँचें। देखें: संपादकीय नीति और अस्वीकरण.