Function $interpolate

test/angular/1.5/angular.js:12590–12701

* @ngdoc service * @name $interpolate * @kind function * * @requires $parse * @requires $sce * * @description * * Compiles a string with markup into an interpolation function. This service is used by the * HTML ng.$compile $compile service fo

(text, mustHaveExpression, trustedContext, allOrNothing)

     * - `context`: evaluation context for all expressions embedded in the interpolated text
     */
    function $interpolate(text, mustHaveExpression, trustedContext, allOrNothing) {
      // Provide a quick exit and simplified result function for text with no interpolation
      if (!text.length || text.indexOf(startSymbol) === -1) {
        var constantInterp;
        if (!mustHaveExpression) {
          var unescapedText = unescapeText(text);
          constantInterp = valueFn(unescapedText);
          constantInterp.exp = text;
          constantInterp.expressions = [];
          constantInterp.$$watchDelegate = constantWatchDelegate;
        }
        return constantInterp;
      }

      allOrNothing = !!allOrNothing;
      var startIndex,
          endIndex,
          index = 0,
          expressions = [],
          parseFns = [],
          textLength = text.length,
          exp,
          concat = [],
          expressionPositions = [];

      while (index < textLength) {
        if (((startIndex = text.indexOf(startSymbol, index)) !== -1) &&
             ((endIndex = text.indexOf(endSymbol, startIndex + startSymbolLength)) !== -1)) {
          if (index !== startIndex) {
            concat.push(unescapeText(text.substring(index, startIndex)));
          }
          exp = text.substring(startIndex + startSymbolLength, endIndex);
          expressions.push(exp);
          parseFns.push($parse(exp, parseStringifyInterceptor));
          index = endIndex + endSymbolLength;
          expressionPositions.push(concat.length);
          concat.push('');
        } else {
          // we did not find an interpolation, so we have to add the remainder to the separators array
          if (index !== textLength) {
            concat.push(unescapeText(text.substring(index)));
          }
          break;
        }
      }

      // Concatenating expressions makes it hard to reason about whether some combination of
      // concatenated values are unsafe to use and could easily lead to XSS.  By requiring that a
      // single expression be used for iframe[src], object[src], etc., we ensure that the value
      // that's used is assigned or constructed by some JS code somewhere that is more testable or
      // make it obvious that you bound the value to some user controlled value.  This helps reduce
      // the load when auditing for XSS issues.
      if (trustedContext && concat.length > 1) {
          $interpolateMinErr.throwNoconcat(text);
      }

      if (!mustHaveExpression || expressions.length) {
        var compute = function(values) {