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17 of 22JavaScript: Promise
📌 What is a Promise?
A Promise in JavaScript is an object that represents the eventual completion (or failure) of an asynchronous operation and its resulting value. It has three states: pending, fulfilled, and rejected.
1️⃣ Basic Promise Using Variable
Here, a boolean variable controls whether the Promise resolves or rejects.
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2️⃣ Promise Using Function with Parameter
A function returns a Promise, which resolves or rejects based on the parameter value.
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3️⃣ Handling Resolved and Rejected Promises
.then() handles resolved results, and .catch() handles rejections.
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4️⃣ Display 'Fetching...' Before Promise Resolves
Use console.log() before the asynchronous task to simulate a real-world fetch operation.
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5️⃣ Simplified Promise with Chaining
Combining .then() and .catch() directly improves code readability.
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6️⃣ Real-Life Example with AJAX (jQuery)
This Promise wraps a jQuery AJAX call to simulate real-world API usage.
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🧠 Test Your Knowledge
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Keep Going!AJS - Promise.all()