string.js

/**
 * Copyright 2015 The AMP HTML Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @param {string} name Attribute name with dashes
 * @return {string} Dashes removed and character after to upper case.
 * visibleForTesting
 */
export function dashToCamelCase(name) {
  return name.replace(/-([a-z])/g, function(_all, character) {
    return character.toUpperCase();
  });
}

/**
 * Polyfill for String.prototype. endsWith.
 * @param {string} string
 * @param {string} suffix
 * @return {boolean}
 */
export function endsWith(string, suffix) {
  if (suffix.length > string.length) {
    return false;
  }
  const index = string.length - suffix.length;
  return string.indexOf(suffix, index) == index;
}

/**
 * Polyfill for String.prototype. startsWith.
 * @param {string} string
 * @param {string} prefix
 * @return {boolean}
 */
export function startsWith(string, prefix) {
  if (prefix.length > string.length) {
    return false;
  }
  return string.lastIndexOf(prefix, 0) == 0;
}

/**
 * Expands placeholders in a given template string with values.
 *
 * Placeholders use ${key-name} syntax and are replaced with the value
 * returned from the given getter function.
 *
 * @param {string} template The template string to expand.
 * @param {!function(string):*} getter Function used to retrieve a value for a
 *   placeholder. Returns values will be coerced into strings.
 * @param {number=} opt_maxIterations Number of times to expand the template.
 *   Defaults to 1, but should be set to a larger value your placeholder tokens
 *   can be expanded to other placeholder tokens. Take caution with large values
 *   as recursively expanding a string can be exponentially expensive.
 */
export function expandTemplate(template, getter, opt_maxIterations) {
  const maxIterations = opt_maxIterations || 1;
  for (let i = 0; i < maxIterations; i++) {
    let matches = 0;
    template = template.replace(/\${([^}]*)}/g, (_a, b) => {
      matches++;
      return getter(b);
    });
    if (!matches) {
      break;
    }
  }
  return template;
}