node_modules/csso/lib/replace/property/font-weight.js

export default function compressFontWeight(node) {
    const value = node.children.head.data;

    if (value.type === 'Identifier') {
        switch (value.name) {
            case 'normal':
                node.children.head.data = {
                    type: 'Number',
                    loc: value.loc,
                    value: '400'
                };
                break;
            case 'bold':
                node.children.head.data = {
                    type: 'Number',
                    loc: value.loc,
                    value: '700'
                };
                break;
        }
    }
};