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JavaScript Symbol.isConcatSpreadable symbol
The Symbol.isConcatSpreadable symbol is used to specify if a nested array should be flattened to its individual array elements or not when using the Array.prototype.concat() method.
Following is the code for Symbol.isConcatSpreadable symbol −
Example
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
body {
font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}
div {
font-size: 20px;
font-weight: 500;
}
.result {
color: red;
}
</style>
</head>
<body>
<h1>JavaScript Symbol.isConcatSpreadable symbol</h1>
<div class="sample"></div>
<button class="Btn">CLICK HERE</button>
<h3>
Click on the above button to concat the both array into a single one
</h3>
<div class="result">isConcatSpreadable = true</div>
<div class="result">isConcatSpreadable = False</div>
<script>
let fillEle = document.querySelector(".sample");
let result = document.querySelectorAll(".result");
let ele = [1, 2, 3];
let ele2 = ["A", "B", "C"];
let concatArr;
fillEle.innerHTML += ele + "<br>" + ele2 + "<br>";
document.querySelector(".Btn").addEventListener("click", () => {
concatArr = ele.concat(ele2);
for (let x of concatArr.entries()) {
result[0].innerHTML += x + " - ";
}
result.innerHTML += "<br><br>";
ele2[Symbol.isConcatSpreadable] = false;
concatArr = ele.concat(ele2);
for (let x of concatArr.entries()) {
result[1].innerHTML += x + " - ";
}
});
</script>
</body>
</html>Output
On clicking the “CLICK HERE” button −
Updated on: 08-May-2020
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