7 CSS Interview Questions Every Hiring Manager Should Ask

• The red, green, and blue values are integers.
• Each color component value ranges from 0 to 255, inclusive.

    constructor(red, green, blue) {

        this.red = red;

        this.green = green;

        this.blue = blue;

    }

    toCSS() {

        return `rgb(${this.red}, ${this.green}, ${this.blue})`;

    }

}

• Not validating the input values to ensure they are within the 0-255 range.
• Incorrectly formatting the output string in toCSS() method.

• How would you extend this class to support RGBA format?
• Can you implement a method to lighten or darken the color?

• Understanding of CSS color properties.
• Ability to apply object-oriented programming concepts in JavaScript.
• Skill in creating a class that models a real-world concept with practical utility.

This question effectively evaluates a developer’s grasp of both CSS and JavaScript, particularly their ability to intertwine styling with programming logic. It’s an excellent way to assess a candidate’s proficiency in front-end development skills.

• The CSS selector must be a valid string selector.
• The style object should contain at least one property-value pair.

    let elements = document.querySelectorAll(selector);

    for (let i = 0; i < elements.length; i++) {

        for (let style in styles) {

            elements[i].style[style] = styles[style];

        }

    }

}

• Forgetting to handle the case when no elements match the selector.
• Not correctly mapping JavaScript style object properties to CSS properties (e.g., fontWeight in JavaScript vs font-weight in CSS).

• How would you modify this function to add !important to all styles?
• Can this function be optimized for better performance?

• Understanding of manipulating the Document Object Model (DOM) using JavaScript.
• Knowledge of applying CSS styles through JavaScript.
• Familiarity with JavaScript functions and loops.

This question is excellent for assessing a candidate’s ability to integrate JavaScript and CSS, a key skill in front-end web development. It tests the practical application of DOM manipulation, a fundamental concept for creating dynamic and interactive web pages.

• The id must correspond to an existing HTML element.
• The rotation angle should be a valid number.

    let element = document.getElementById(id);

    element.style.transform = `rotate(${angle}deg)`;

}

• Not checking if the element exists before applying the transformation.
• Confusion between rotation degrees and other units (e.g., radians).

• How can this function be adapted to include smooth transition animations?
• What other transformations could be combined with rotation?

• Familiarity with CSS transformations, particularly rotation.
• Ability to manipulate HTML elements using JavaScript.
• Understanding how CSS and JavaScript can be used together to create dynamic effects.

This question effectively evaluates a developer’s skills in both CSS and JavaScript. It tests their ability to use CSS transformations, an important aspect of creating engaging and interactive web interfaces. The task also emphasizes the practical application of JavaScript for DOM manipulation.

• Both rows and columns must be positive integers.

    let grid = document.createElement(‘div’);

    grid.style.display = ‘grid’;

    grid.style.gridTemplateRows = `repeat(${rows}, 1fr)`;

    grid.style.gridTemplateColumns = `repeat(${columns}, 1fr)`;

    for (let i = 0; i < rows * columns; i++) {

        let cell = document.createElement(‘div’);

        cell.textContent = `Cell ${i + 1}`;

        grid.appendChild(cell);

    }

    return grid;

}

• Not setting the correct grid layout properties can lead to an incorrect structure.
• Forgetting to add each cell to the grid container.
• Overlooking the need to handle large numbers of rows and columns efficiently.

• How would you modify the function to allow different sizes for rows and columns?
• Could you add functionality to handle grid-gap or cell styling?

• Knowledge of the CSS grid layout, an essential skill for creating responsive designs.
• Ability to dynamically generate and manipulate HTML elements using JavaScript.
• Understanding of combining JavaScript and CSS to create complex web layouts.

This question is particularly relevant for front-end development roles, where creating responsive and aesthetically pleasing layouts is a common task. It tests a blend of JavaScript and CSS skills, focusing on dynamic element creation and advanced CSS styling.

• The browser window’s width is assumed to be a positive number.

    let div = document.createElement(‘div’);

    let style = document.createElement(‘style’);

    style.innerHTML = `

        #responsiveDiv {

            width: 100%;

        }

        @media (min-width: 600px) {

            #responsiveDiv {

                width: 50%;

            }

        }

    `;

    document.head.appendChild(style);

    div.id = “responsiveDiv”;

    return div;

}

• Forgetting to append the style element to the document would result in the styles not being applied.
• Incorrectly setting up the media query leads to improper responsive behavior.
• Not considering other CSS properties that might affect the responsiveness, like box-sizing.

• How would you handle different styles for portrait and landscape orientations?
• What additional features would you add to make the div more interactive or visually appealing?

• Understanding of CSS media queries for implementing responsive designs.
• Ability to dynamically create and manipulate HTML and CSS using JavaScript.
• Conceptual knowledge of responsive design principles.

This question effectively gauges a candidate’s skill in creating responsive web designs, a critical aspect of modern web development. It tests their technical knowledge of CSS and JavaScript and their understanding of designing web pages that adapt to different screen sizes and orientations.

• The id must correspond to an existing HTML element.

    let element = document.getElementById(id);

    let style = document.createElement(‘style’);

    style.innerHTML = `

        @keyframes colorChange {

            0% {background-color: red;}

            100% {background-color: blue;}

        }

        #${id} {

            animation: colorChange 5s;

        }

    `;

    document.head.appendChild(style);

}

• Not correctly defining the keyframes in the CSS.
• Forgetting to append the style tag to the document, resulting in the animation not being applied.
• Not handling potential conflicts with other existing styles or animations on the element.

• How would you modify the function to include easing functions for the animation?
• Can this function be extended to support other types of animations or multiple elements?

• Understanding of CSS keyframe animations and their implementation.
• Ability to manipulate HTML elements and CSS using JavaScript.
• Knowledge of creating dynamic and engaging visual effects using CSS.

This question is a great way to assess a developer’s skills in creating advanced visual effects with CSS animations, a key component in modern, interactive web design. It tests the integration of JavaScript and CSS for dynamic style manipulation, a common requirement in web development projects.

• The id must correspond to an existing HTML element.
• The color must be a valid CSS color.

    let element = document.getElementById(id);

    element.style.setProperty(‘–theme-color’, color);

}

• Not ensuring that the specified element exists in the document.
• Using an incorrect method to set the CSS variable value.
• Not handling different formats of CSS color values properly.

• How would you extend this function to modify multiple CSS variables at once?
• Can you adapt this function to apply the theme change to the entire webpage rather than just one element?

• Knowledge of CSS Variables (custom properties) and their manipulation through JavaScript.
• Ability to dynamically modify styles in response to user interactions or other conditions.
• Understanding of more advanced CSS features and how they interact with JavaScript.

This question challenges a candidate’s ability to integrate JavaScript with advanced CSS features. CSS variables are increasingly important in modern web design for creating maintainable, scalable, and dynamic styles. This task tests both technical skills and conceptual understanding of these contemporary web development practices.