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Multiply only specific value in a JavaScript object?
The ability to multiply only specific values in a JavaScript object can be a useful tool for performing calculations or making modifications to data. By using methods like map(), forEach(), and traditional loops, you can efficiently target and modify values that meet certain criteria.
An object in JavaScript is a separate entity having properties and a type. This article demonstrates various approaches to selectively multiply values within objects and arrays.
Method 1: Using Array.map() to Transform Object Properties
In this example, we multiply the value property of each object in an array by 3:
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<script>
let someArray = [
{"car":"BMW", "value":34},
{"car":"BENZ", "value":80},
{"car":"AUDI", "value":75}
];
let result = someArray.map(data => {
return {...data, value: data.value * 3}
});
document.getElementById("tutorial").innerHTML = JSON.stringify(result);
</script>
</body>
</html>
[{"car":"BMW","value":102},{"car":"BENZ","value":240},{"car":"AUDI","value":225}]
Method 2: Using Object.values() and forEach()
This approach uses Object.values() to iterate through nested objects and multiply specific array elements:
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<script>
let fundata = {
'arr1': {
a: [2, 3],
b: []
},
'arr2': {
a: [5, 6],
b: []
}
};
let multiplier = 50;
Object.values(fundata).forEach(item => {
item.a = item.a.map(number => number * multiplier);
});
document.getElementById("tutorial").innerHTML = JSON.stringify(fundata);
</script>
</body>
</html>
{"arr1":{"a":[100,150],"b":[]},"arr2":{"a":[250,300],"b":[]}}
Method 3: Combining Array.map() and Array.reduce()
This example multiplies object properties to calculate areas, then sums the results:
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<p id="tutorial1"></p>
<script>
var array = [
{ x: 10, y: 30 },
{ x: 20, y: 90 },
{ x: 54, y: 32 }
];
var areas = array.map(arr => arr.x * arr.y);
var total = areas.reduce((a, b) => (a + b));
document.getElementById("tutorial").innerHTML = "Areas: " + JSON.stringify(areas);
document.getElementById("tutorial1").innerHTML = "Total: " + total;
</script>
</body>
</html>
Areas: [300,1800,1728] Total: 3828
Method 4: Conditional Multiplication Using for Loop
This approach multiplies values only when they meet specific criteria:
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<p id="tutorial1"></p>
<p id="tutorial2"></p>
<p id="tutorial3"></p>
<script>
var employee = [
{ name: "John", amount: 800 },
{ name: "David", amount: 500 },
{ name: "Bob", amount: 450 }
];
document.getElementById("tutorial").innerHTML = "Before multiplying:";
document.getElementById("tutorial1").innerHTML = JSON.stringify(employee);
// Multiply amount by 2 only if greater than 500
for (var index = 0; index < employee.length; index++) {
if (employee[index].amount > 500) {
employee[index].amount = employee[index].amount * 2;
}
}
document.getElementById("tutorial2").innerHTML = "After multiplying:";
document.getElementById("tutorial3").innerHTML = JSON.stringify(employee);
</script>
</body>
</html>
Before multiplying:
[{"name":"John","amount":800},{"name":"David","amount":500},{"name":"Bob","amount":450}]
After multiplying:
[{"name":"John","amount":1600},{"name":"David","amount":500},{"name":"Bob","amount":450}]
Comparison of Methods
| Method | Use Case | Modifies Original | Returns New Object |
|---|---|---|---|
Array.map() |
Transform all elements | No | Yes |
Object.values() + forEach() |
Modify nested objects | Yes | No |
for loop |
Conditional modifications | Yes | No |
Conclusion
JavaScript provides multiple approaches to multiply specific values in objects. Use Array.map() for creating new transformed arrays, forEach() for modifying existing objects, and traditional loops for conditional operations. Choose the method that best fits your specific use case and data structure.
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