How to sum javascript attributes

JavaScript is a very important programming language that is widely used in web development, server-side programming and other fields. One common requirement is to sum the properties of an object, which is the topic of this article.

Before we begin, let’s look at a simple example. Suppose there is an object person, which has two attributes name and age. Now we want to find the total age of this object, how to do it?

var person1 = {name: "Alice", age: 23}
var person2 = {name: "Bob", age: 25}
var person3 = {name: "Charlie", age: 27}

var sum = person1.age + person2.age + person3.age;
console.log(sum); // 输出结果为：75

In the above example, we obtain the sum by adding the age attribute of each person one by one to the variable sum. However, this method is not feasible when the number of attributes is large. Therefore, we need to use some more efficient and convenient methods.

Next, we will demonstrate three different methods to solve for the sum of all numeric properties in an object. These three methods are:

1. Simple loop summation method
2. Object.keys() combined with array reduce() method
3. for...in Combining loops with the hasOwnProperty() method

We will explain each method in detail.

Method 1: Simple loop summation method

This method is the most direct method. It traverses all the attributes in the object, filters out the attributes with numerical values, and then compares them one by one. add. The following is the code implementation:

function sumProperties(obj) {
  var sum = 0;
  for (var prop in obj) {
    if (typeof obj[prop] === 'number') {
      sum += obj[prop];
    }
  }
  return sum;
}

var person = {
  name: 'Alice',
  age: 23,
  salary: 5000.00
};

var total = sumProperties(person);
console.log(total); // 输出结果为：5023

The above code defines a sumProperties() function, whose parameter is an object. In the function, we use a for...in loop to iterate through all the properties in the object. If the value of the attribute is a number, add it to the variable sum. Finally, the function returns the variable sum as the return value to the caller.

This method is simple and clear, suitable for small-scale objects. But if you want to deal with large-scale objects (such as hundreds of properties), this will be very time-consuming.

Method 2: Combining Object.keys() with the array reduce() method

Object.keys() is a very practical method in JavaScript. It is used to obtain all the keys in an object. Property name (excluding inherited properties). Combined with the array reduce() method, we can easily sum the properties in an object. The following is the code implementation:

function sumProperties(obj) {
  return Object.keys(obj).reduce(function(sum, key) {
    return typeof obj[key] === 'number' ? sum + obj[key] : sum;
  }, 0);
}

var person = {
  name: 'Alice',
  age: 23,
  salary: 5000.00
};

var total = sumProperties(person);
console.log(total); // 输出结果为：5023

In the above code, the sumProperties() function is similar to the previous method. In the function, we use the Object.keys() method to get an array of all property names in the object. Then, we call the reduce() method of the array and add each item in the array to the variable sum. If the value of the attribute is not a number, we do nothing with the variable sum and leave it as is. Finally, we return the variable sum to the caller as the return value of the function.

Method 3: Combining the for...in loop with the hasOwnProperty() method

This method combines the for...in loop with the hasOwnProperty() method in JavaScript to filter Remove inherited properties from the object. The code implementation is as follows:

function sumProperties(obj) {
  var sum = 0;
  for (var prop in obj) {
    if (obj.hasOwnProperty(prop)) {
      if (typeof obj[prop] === 'number') {
        sum += obj[prop];
      }
    }
  }
  return sum;
}

var person = {
  name: 'Alice',
  age: 23,
  salary: 5000.00
};

var total = sumProperties(person);
console.log(total); // 输出结果为：5023

In the above code, we modified the code of the first method. In the for...in loop, we use the hasOwnProperty() method to filter out inherited properties. This method is more general and suitable for most situations. However, it should be noted that this method cannot handle the case where the attribute name contains special characters such as spaces.

Conclusion

The above three methods can meet the needs of most cases. However, it should be noted that these methods are not perfect and they may cause problems in some special cases. But if we better understand how they work, and what their strengths and weaknesses are, we can use them better.

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